Design and Synthesis of Novel Caudatin Derivatives Containing Arylacryloyl and Quinolyl Substituents With Anticancer Activity

Xiao‐San Li; He‐Hui Zhan; Xin‐Hong Wang; Tong‐Xin Zheng; Bing‐Bing Li; Hui‐Ting Chen; An‐Yu Su; Li Liu; Xue‐Mei Yang; Hui Luo

doi:10.1002/cbdv.71821

. 2026 Oct 15;23(10):e71821. doi: 10.1002/cbdv.71821

Design and Synthesis of Novel Caudatin Derivatives Containing Arylacryloyl and Quinolyl Substituents With Anticancer Activity

Xiao‐San Li ^1,^✉,^#, He‐Hui Zhan ^1,^2,^#, Xin‐Hong Wang ^1,³, Tong‐Xin Zheng ¹, Bing‐Bing Li ³, Hui‐Ting Chen ³, An‐Yu Su ⁴, Li Liu ³, Xue‐Mei Yang ^3,^✉, Hui Luo ^1,^2,^✉

PMCID: PMC13670407 PMID: 42878227

ABSTRACT

Caudatin (1) represents one of major C₂₁‐steroids isolated from Cynanchum otophyllum. Thirty‐one novel caudatin derivatives with arylacryloyl (1a–1w) and quinolyl (2a–2h) substituents were synthesized and structurally characterized by spectroscopic analysis. Their anticancer activities were evaluated against four human cancer cell lines (MCF‐7, H1299, HeLa, and HepG2). Most compounds exhibit significant antiproliferative effects, among which 1b and 2h demonstrated broad‐spectrum activity with IC₅₀ values of 8.54–12.12 and 11.43–14.25 uM, respectively. Further mechanistic studies showed that 1b induced marked apoptosis in HepG2 cells and modulated cell cycle distribution, with a higher percentage of cells accumulating in the G0/G1 phase at increased concentrations. Overall, these findings indicate that caudatin derivatives bearing arylacryloyl and quinolyl moieties constitute a preliminary chemical framework for the development of antitumor candidates for caudatin‐like natural products.

Keywords: anticancer activity, arylacryloyl and quinolyl substituents, caudatin, synthesis

Thirty‐one novel caudatin derivatives with arylacryloyl (1a–1w) and quinolyl (2a–2h) substituents were synthesized. Compounds 1b and 2h demonstrated broad‐spectrum activity with IC₅₀ values of 8.54−12.12 and 11.43−14.25 uM, respectively. Compound 1b induced apoptosis and G0/G1arrest in HepG2 cells.

graphic file with name CBDV-23-e71821-g005.webp

1. Introduction

The C‐17 acetyl group of the C₂₁‐steroid skeleton is a well‐established and versatile modification site for enhancing bioactivity [1, 2, 3, 4, 5, 6, 7], and side‐chain derivatization at this position represents a core strategy for optimizing the pharmacological potency of C₂₁ steroids [8]. Among various modification strategies, the introduction of arylacryloyl and quinolyl pharmacophores has been demonstrated to be an effective approach [9, 10, 11, 12, 13]. Target derivatives with arylacryloyl group exhibit a wide range of bioactivities owing to the presence of the α,β‐unsaturated ketone moiety, including potent antiproliferative and pro‐apoptotic effects [14, 15, 16, 17, 18]. Structure–activity relationship studies on arylacryloyl derivatives have established the α,β‐unsaturated carbonyl moiety as a key anticancer pharmacophore [19]. For steroidal scaffolds, the incorporation of arylacryloyl groups at the C‐17 position via Claisen–Schmidt condensation has been demonstrated to enhance antiproliferative activity compared with the parent steroids [20, 21]. Similarly, quinolyl derivatives, as an important class of heterocyclic scaffolds, are widely used in anticancer drug design due to their ability to intercalate into DNA and inhibit key enzymes such as topoisomerase [10]. The Friedländer condensation, a classic and efficient route to quinoline scaffolds, enables the ready synthesis of structurally diverse quinoline‐conjugated steroid derivatives [22, 23]. Steroid–quinoline hybrids have been demonstrated to exert promising anticancer effects via cell cycle arrest and apoptosis induction, supporting the rationale for this structural modification strategy [24, 25, 26]. In recent years, a variety of steroids bearing arylacryloyl and quinolyl moieties have been successfully synthesized, and many of these compounds show more potent biological activity than the parent drug [27, 28, 29, 30, 31, 32].

C₂₁‐steroids are a class of pregnane derivatives predominantly found in plants of the genus Cynanchum, which have attracted extensive attention due to their potential antitumor, antiepileptic, antidepressant, immunosuppressive, antiaging, and antiviral activities [33]. In our previous studies, caudatin (1), a representative C₂₁‐steroidal aglycone, was isolated from the hydrolysate of Cynanchum otophyllum roots and purified on a large scale by various chromatographic methods [34] (Figure 1). It has been identified as a valuable lead compound and scaffold for antitumor drug development [14, 35, 36, 37]. In this study, a series of novel caudatin derivatives bearing arylacryloyl (1a–1w) and quinolyl (2a–2h) substituents were synthesized and evaluated for antiproliferative activity against four human cancer cell lines (MCF‐7, H1299, HeLa, and HepG2). Furthermore, the pro‐apoptotic effect and cell cycle arrest induced by compound 1b were investigated to elucidate its mechanism of action.

2. Results and Discussion

2.1. Chemistry

2.1.1. Synthesis of Caudatin Derivatives With Arylacryloyl Substituents (1a–1w)

Caudatin derivatives with arylacryloyl substituents (1a–1w) were synthesized according to the pathways described in Scheme 1. Anhydrous ethanol (EtOH) was mixed with potassium tert‐butoxide (t‐BuOK) at room temperature, and the mixture was sonicated until complete dissolution. Caudatin (1) was then added, and the mixture was stirred continuously until a clear solution formed. Subsequently, aromatic aldehydes with different substituents were added, and the mixture was refluxed at 90°C to promote a Claisen–Schmidt condensation, yielding a series of target products. All the products were purified by semi‐preparative RP‐HPLC eluted with MeOH/H₂O, and their purity was determined by HPLC analysis (Figures S94–S116). Their structures were elucidated by spectroscopic analysis, including ¹H and ¹³C NMR and HR‐MS‐ESI (Figures S1–S69).

Mechanistically, the active methyl group of the acetyl moiety on C‐17 of caudatin (1) was deprotonated by t‐BuOK in anhydrous ethanol, generating a nucleophilic enolate. This enolate then underwent a base‐catalyzed cross‐aldol addition with the aldehyde group of the corresponding aromatic aldehyde, followed by dehydration of the intermediate β‐hydroxy ketone. Under these strong‐base reflux conditions, the condensation proceeds via thermodynamic control, resulting in the exclusive formation of the thermodynamically favored E‐configured α, β‐unsaturated double bond. No Z‐isomer was isolated from any of the reaction mixtures.

2.1.2. Synthesis of Caudatin Derivatives With Quinolyl Substituents (2a–2h)

Similarly, as outlined in Scheme 2, a series of caudatin derivatives with quinolyl substituents (2a–2h) was also successfully synthesized via a modified Friedländer quinoline synthesis, employing 2‐amino aromatic aldehydes and the steroidal ketone of caudatin (1) as key building blocks. In this transformation, the active methyl group of the acetyl moiety on C‐17 of caudatin (1) was deprotonated by t‐BuOK in anhydrous EtOH, generating a nucleophilic enolate that underwent a base‐catalyzed condensation with the formyl group of the corresponding 2‐aminobenzaldehyde derivatives. Subsequent intramolecular cyclization, dehydration, and aromatization afforded the fused quinoline ring. All the products were purified by semi‐preparative RP‐HPLC eluted with MeOH/H₂O, and their purity was determined by HPLC analysis (Figures S117–S124). Their structures were elucidated by spectroscopic analysis, including ¹H and ¹³C NMR and HR‐MS‐ESI (Figures S70–S93).

2.2. Biological Evaluation

2.2.1. Antiproliferative Activities and Structure–Activity Relationships

The antiproliferative activities of all compounds were evaluated by MTT assay against MCF‐7, H1299, HeLa, and HepG2 cells, with colchicine used as a positive control. As shown in Table 1, most of the arylacryloyl caudatin derivatives exhibited good antiproliferative activity (IC₅₀ < 40 µM), except 1i. Among them, 1b displayed the most potent activity, especially HepG2 cells (IC₅₀ = 8.54 µM), and derivatives bearing halogen substituents also exhibited good activity (e.g., 1o–1w). Meanwhile, with the exception of 2c and 2g, most of the quinolyl caudatin derivatives exhibited moderate to good antiproliferative activity (IC₅₀ = 11.43–49.43 µM), while 2h exhibited the most potent activity. Among the arylacryloyl derivatives, analogs bearing five‐membered heterocyclic substituents generally exhibited more potent antiproliferative activity than those with six‐membered ones (e.g., 1b > 1d and 1e). Broadly, analogs with electron‐withdrawing groups generally showed more favorable activity, although not uniformly. For instance, the methoxy‐substituted analog 1g, bearing an electron‐donating group, was highly potent (14.46–19.55 µM), outperforming strong electron‐withdrawing analogs, including 1l (─CN), 1m (─NO₂), and 1n (─CF₃). Among the halogen‐substituted arylacryloyl derivatives, fluorinated analogs generally displayed well‐balanced antiproliferative activity across all four cancer cell lines, with mono‐fluorinated analogs following a para (1o) > meta (1p) > ortho (1q) potency order. The number of fluorine substituents also influenced activity, with 1t (3,5‐difluoro‐substituted) being the most active among the polyfluorinated analogs. In the quinolyl series, introducing halogen atoms onto the quinoline ring generally enhanced antiproliferative activity. Bromine substitution, particularly the dibromo substitution pattern in 2h, conferred the most pronounced potency improvement, followed by chlorine substitution, whereas fluorine substitution only marginally increased activity. Notably, the quinoline derivative 2a still retained moderate activity against H1299 and HepG2 cells (IC₅₀ = 16.59 and 17.04 µM, respectively), indicating that the quinoline scaffold itself imparts measurable bioactivity and that halogenation serves as an optimization strategy rather than an absolute prerequisite for activity. Compound 2h emerged as the optimal derivative in this series, displaying potent broad‐spectrum antiproliferative activity with moderately higher growth inhibitory potency against HepG2 cells (IC₅₀ = 11.43 µM).

TABLE 1.

Cytotoxicity of all synthetic products (IC₅₀ values expressed in µM).

Compound	R	Cell lines
Compound	R	MCF‐7	H1299	HeLa	HepG2
1		> 40	> 40	> 40	> 40
1a		21.53 ± 2.12	24.14 ± 2.82	25.69 ± 0.72	26.82 ± 1.54
1b		10.94 ± 0.81	12.12 ± 0.96	10.77 ± 1.17	8.54 ± 1.34
1c		19.66 ± 0.99	20.18 ± 0.92	20.09 ± 0.84	18.12 ± 1.03
1d		39.88 ± 4.63	36.21 ± 3.08	> 40	38.72 ± 1.97
1e		23.66 ± 1.25	27.93 ± 1.20	27.99 ± 1.94	28.91 ± 1.14
1f		28.07 ± 2.34	33.61 ± 2.35	29.80 ± 2.83	23.75 ± 1.88
1g		14.46 ± 0.69	16.46 ± 0.90	19.55 ± 1.01	16.12 ± 0.88
1h		19.32 ± 1.74	23.02 ± 2.31	23.50 ± 1.92	16.16 ± 0.87
1i		> 40	> 40	> 40	> 40
1j		23.06 ± 2.78	25.92 ± 3.65	23.47 ± 1.67	18.95 ± 2.41
1k		39.98 ± 1.87	44.84 ± 2.05	39.31 ± 2.12	41.52 ± 2.17
1l		28.95 ± 1.06	23.35 ± 1.94	27.62 ± 1.91	22.40 ± 1.31
1m		26.92 ± 1.66	25.70 ± 1.28	31.58 ± 1.53	28.21 ± 1.92
1n		19.02 ± 1.09	16.28 ± 1.49	20.53 ± 1.55	21.79 ± 1.98
1o		13.16 ± 1.08	12.94 ± 1.24	14.29 ± 2.58	14.88 ± 1.72
1p		16.56 ± 0.90	15.62 ± 0.62	18.85 ± 1.05	13.00 ± 0.21
1q		21.94 ± 1.44	15.96 ± 0.51	22.26 ± 0.76	13.55 ± 0.92
1r		23.03 ± 2.17	22.38 ± 0.68	19.72 ± 0.81	17.77 ± 1.25
1s		27.90 ± 0.96	20.05 ± 1.17	28.50 ± 1.34	18.72 ± 0.73
1t		15.46 ± 0.15	14.33 ± 0.32	14.19 ± 0.77	11.91 ± 0.28
1u		15.64 ± 0.21	13.17 ± 0.39	15.23 ± 0.52	12.42 ± 0.27
1v		21.79 ± 0.95	23.42 ± 1.30	22.06 ± 1.69	21.08 ± 1.14
1w		19.45 ± 0.72	14.17 ± 0.37	17.88 ± 0.33	16.21 ± 0.44
2a		25.72 ± 1.82	16.59 ± 0.81	24.48 ± 1.79	17.04 ± 1.20
2b		46.90 ± 1.88	42.08 ± 1.67	49.43 ± 1.88	40.64 ± 2.43
2c		> 40	> 40	> 40	> 40
2d		39.34 ± 1.94	35.52 ± 1.83	36.86 ± 2.76	39.85 ± 1.40
2e		16.50 ± 1.13	15.85 ± 0.92	17.57 ± 1.47	18.17 ± 1.26
2f		15.28 ± 1.25	15.06 ± 0.60	18.16 ± 1.16	14.40 ± 0.95
2g		> 40	39.22 ± 1.75	> 40	> 40
2h		14.25 ± 0.30	13.08 ± 0.68	12.53 ± 0.77	11.43 ± 0.29
Colchicine ^a		0.036 ± 0.004	0.048 ± 0.005	0.119 ± 0.021	0.044 ± 0.006

Open in a new tab

^{^a}

Positive control. IC₅₀ values are presented as the mean ± SD from three independent experiments.

2.2.2. Analysis of Cell Apoptosis

To investigate whether the cytotoxicity of 1b was mediated by apoptosis induction, we evaluated its pro‐apoptotic effect on HepG2 cells using the Annexin V‐fluorescein isothiocyanate (FITC)/propidium iodide (PI) double staining assay. As shown in Figure 2, treatment of HepG2 cells with 1b (5, 10, and 30 µM) for 48 h significantly increased the total proportion of apoptotic cells in a dose‐dependent manner compared with the untreated control group, with the total apoptotic rate rising from 5.95% in the control to 14.06%, 32.1%, and 92.9%, respectively. These results confirmed that 1b could efficiently trigger potent apoptosis in HepG2 cells, demonstrating that its remarkable antiproliferative and cytotoxic activity mainly derives from its pro‐apoptotic effect.

Apoptosis in HepG2 cells was induced by compound 1b. (A) Representative flow cytometry dot plots of HepG2 cells after treatment with 1b at different concentrations (5, 10, and 30 µM) for 48 h. The percentages of cells in each stage of apoptosis were quantified by flow cytometry: necrotic cells (upper left quadrant), late apoptotic cells (upper right quadrant), live cells (lower left quadrant), and early apoptotic cells (lower right quadrant). (B) Histograms displayed the apoptotic ratios of HepG2 cells (% of total). Data are shown as mean ± standard deviation from three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001, compared to control.

2.2.3. Cell Cycle Study by Flow Cytometry

Since cell cycle arrest is an important mechanism underlying the inhibition of cancer cell proliferation, we evaluated the effects of compound 1b on the cell cycle distribution of HepG2 cells using flow cytometry. As shown in Figure 3, when HepG2 cells were treated with 1b (5, 10, and 30 µM) for 48 h, the cell cycle distribution exhibited a marked concentration‐dependent change. In the untreated control, the percentages of cells in the G0/G1, S, and G2/M phases were 45.82%, 33.47%, and 18.02%, respectively. After treatment with 5 µM, the proportion of G2/M phase cells slightly increased to 22.56%, with no obvious alteration in the proportion of G0/G1 and S phase cells. Notably, when the concentration reached 30 µM, the percentage of cells in G0/G1 phase was significantly elevated to 52.84%, with the S and G2/M phase fractions markedly reduced to 21.02% and 7.73%, respectively. Together, these results indicated that compound 1b induces G0/G1 phase arrest in HepG2 cells at higher concentrations.

Cell cycle arrest in HepG2 cells was induced by compound 1b. (A) Cell cycle distribution of HepG2 after treatment with 1b at different concentrations (5, 10, and 30 µM) for 48 h. (B) Histograms displayed the percentages of cells in each phase of the cell cycle after treatment with 1b. Data are expressed as mean ± standard deviation from three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001, compared to control.

3. Conclusions

A series of novel caudatin derivatives with arylacryloyl (1a–1w) and quinolyl (2a–2h) substituents was successfully synthesized via Claisen–Schmidt condensation and Friedländer quinoline synthesis, and their antiproliferative activities were evaluated against four human cancer cell lines. Most compounds exhibited potent antiproliferative effects, among which 1b and 2h showed the strongest activity against HepG2 cells. Mechanistic studies further revealed that 1b induced apoptosis and caused G0/G1 phase arrest in HepG2 cells. Preliminary SAR analysis revealed that the arylacryloyl substituent and the introduction of multiple halogen atoms onto the quinoline ring represent effective strategies for enhancing antitumor activity. Collectively, these findings identified the methyl ketone moiety at C‐17 of C₂₁‐steroidal aglycones as a promising modification site for conferring or enhancing anticancer activity.

4. Experimental Section

4.1. Chemistry

4.1.1. General Information

In our preliminary study, caudatin (1) was isolated from the hydrolysate of the extract derived from the roots of C. otophyllum. Unless otherwise specified, all reagents were obtained from commercial suppliers and used without further purification. For example, aromatic aldehydes, 2‐amino aromatic aldehydes, potassium tert‐butoxide (t‐BuOK), and anhydrous ethanol (EtOH) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (Shanghai, China). Thin‐layer chromatography (TLC) analysis was performed on precoated silica gel GF254 plates (Qingdao Haiyang Chemical Group Co., Qingdao, China). Reaction progress was monitored by heating after treatment with a 5% vanillin‐sulfuric acid solution and/or by UV detection. NMR spectra were recorded on a Bruker AV 400 spectrometer (¹H at 400 MHz, ¹³C at 100 MHz). Chemical shifts are reported in δ (ppm) relative to the solvent residual peaks, using CDCl₃ or pyridine‐d ₅ (Cambridge Isotope Laboratories, MA, USA) containing 0.05% (v/v) tetramethylsilane (TMS) as the internal standard. Chemical shifts are reported to the solvent peak signals (δ _H 7.26 and δ _C 77.2 ppm for CDCl₃; δ _H 7.58 and δ _C 135.9 ppm for pyridine‐d ₅), and coupling constants (J) are given in hertz. Analytical high‐performance liquid chromatography (HPLC) was performed on an Agilent Technologies 1260 Infinity II system (Germany) equipped with an Agilent C₁₈ analytical column (4.6 × 150 mm, 5 µm, USA). Semi‐preparative HPLC was conducted on an Agilent Technologies 1260 Infinity system (Germany) fitted with a quaternary pump, autosampler, diode array detector (DAD), and an Agilent C₁₈ semi‐preparative column (10 × 150 mm, 5 µm, USA). HR‐ESI‐MS and ESI‐MS data were acquired on a Micromass Q‐TOF and SCIEX Triple Quad 4500 mass spectrometer, respectively.

4.1.2. General Procedure for Synthesis of Caudatin Derivatives With Arylacryloyl Substituents (1a–1w)

Anhydrous ethanol (10 mL) was mixed with t‐BuOK (2.0 equiv.) at room temperature and sonicated to dissolve, followed by the addition of caudatin (1, 1.0 equiv.). The mixture was stirred until a clear solution was obtained. Subsequently, aromatic aldehydes with different substituents (3.5 equiv.) were added. The resulting mixture was stirred under reflux at 90°C until no starting material was observed by TLC (approximately 2 h). After the reaction was completed, the mixture was concentrated under reduced pressure, diluted with ethyl acetate (EtOAc), and washed successively with 1 M HCl, a saturated NaHCO₃ solution, and water. The resulting organic layer was dried over anhydrous Na₂SO₄, and then concentrated under reduced pressure to afford the crude product. The crude product was purified by semi‐preparative reversed‐phase high‐performance liquid chromatography (RP‐HPLC, 65%–85% MeOH–H₂O) to obtain the target arylacryloyl derivatives (1a–1w).

4.1.2.1. (21E)‐21‐(Furan‐2‐ylmethylene)‐Caudatin (1a)

Obtained as a yellow solid (23.1 mg, 38.5%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.48 (1H, s), 7.30 (1H, d, J = 15.8 Hz), 7.02 (1H, d, J = 15.8 Hz), 6.60 (1H, s), 6.45 (1H, s), 5.37 (1H, s), 5.31 (1H, s), 4.65–4.71 (3H, m), 3.52–3.58 (1H, m), 2.83–2.86 (1H, t, J = 13.1 Hz), 2.53 (1H, s), 2.31–2.34 (2H, m), 2.21 (2H, s), 1.90–2.16 (5H, m), 1.86 (3H, s), 1.79–1.84 (4H, m), 1.53–1.56 (2H, m), 1.34 (3H, s), 1.14 (3H, s), 1.07–1.10 (1H, m), 0.89 (6H, d, J = 6.8 Hz) (Figure S1); ¹³C NMR (100 MHz, CDCl₃): δc 198.3 (C‐20), 166.9 (C‐1′), 166.2 (C‐3′), 151.7 (C‐2″), 145.2 (C‐5″), 140.1 (C‐5), 129.5 (C‐22), 118.6 (C‐21), 118.3 (C‐6), 116.3 (C‐3″), 113.5 (C‐2′), 112.7 (C‐4″), 91.1 (C‐17), 87.9 (C‐14), 74.2 (C‐8), 72.0 (C‐3, C‐12), 58.9 (C‐13), 43.7 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.6 (C‐15), 34.2 (C‐7), 31.6 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′, C‐6′), 18.5(C‐19), 16.1 (C‐7′), 9.8 (C‐18) (Figure S2 and Table S1); (+)‐HR‐ESI‐MS m/z 569.3112 [M + H]⁺ (calcd for C₃₃H₄₅O₈, 569.3114) (Figure S3).

4.1.2.2. (21E)‐21‐(Thiophen‐2‐ylmethylene)‐Caudatin (1b)

Obtained as a yellow solid (21.2 mg, 34.7%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.67 (1H, d, J = 15.8 Hz), 7.39 (1H, d, J = 4.0 Hz), 7.27 (1H, s), 7.02–7.05 (1H, m), 6.97 (1H, d, J = 15.8 Hz), 5.38 (1H, s), 5.34 (1H, s), 4.69–4.73 (2H, m), 4.63 (1H, s), 3.52–3.60 (1H, m), 2.88 (1H, t, J = 13.5 Hz), 2.51 (1H, s), 2.33–2.36 (2H, m), 2.23 (2H, s), 1.97–2.17 (5H, m), 1.89 (3H, s), 1.81–1.84 (4H, m), 1.55–1.58 (2H, m), 1.36 (3H, s), 1.15 (3H, s), 1.10–1.13 (1H, m), 0.87 (6H, d, J = 6.8 Hz) (Figure S4); ¹³C NMR (100 MHz, CDCl₃): δc 198.1 (C‐20), 167.0 (C‐1′), 166.3 (C‐3′), 140.3 (C‐22), 140.1 (C‐5), 135.9 (C‐2″), 131.9 (C‐5″), 129.2 (C‐3″), 128.2 (C‐4″), 119.9 (C‐21), 118.2 (C‐6), 113.5 (C‐2′), 91.1 (C‐17), 88.0 (C‐14), 74.2 (C‐8), 72.0 (C‐12), 71.9 (C‐3), 58.8 (C‐13), 43.7 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.6 (C‐15), 34.1 (C‐7), 31.7 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.8 (C‐6′), 18.5 (C‐19), 16.1 (C‐7′), 9.8 (C‐18) (Figure S5 and Table S1); (+)‐HR‐ESI‐MS m/z 585.2891 [M + H]⁺ (calcd for C₃₃H₄₅O₇S, 585.2886) (Figure S6).

4.1.2.3. (21E)‐21‐Benzylidene‐Caudatin (1c)

Obtained as a yellow solid (26.5 mg, 41.1%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.58 (1H, d, J = 15.6 Hz), 7.52 (2H, d, J = 7.3 Hz), 7.35 (3H, m), 7.14 (1H, d, J = 15.6 Hz), 5.38 (1H, s), 5.29 (1H, s), 4.73–4.78 (3H, m), 3.53–3.59 (1H, m), 2.87 (1H, t, J = 13.0 Hz), 2.58 (1H, s), 2.32–2.35 (2H, m), 2.22 (2H, s), 1.82–2.10 (9H, m), 1.79 (3H, s), 1.54–1.57 (2H, m), 1.34 (3H, s), 1.15 (3H, s), 1.10–1.13 (1H, m), 0.77 (6H, d, J = 6.9 Hz) (Figure S7); ¹³C NMR (100 MHz, CDCl₃): δc 198.5 (C‐20), 167.3 (C‐1′), 166.4 (C‐3′), 143.8 (C‐22), 140.0 (C‐5), 134.5 (C‐1″), 130.8 (C‐4″), 128.9 (C‐2″, C‐3″, C‐5″, C‐6″), 120.6 (C‐21), 118.4 (C‐6),113.5 (C‐2′), 91.2 (C‐17), 87.9 (C‐14), 74.1 (C‐8), 72.1 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 43.7 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 36.9 (C‐10), 34.6 (C‐15), 34.3 (C‐7), 31.5 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.7 (C‐5′), 20.7 (C‐6′), 18.5 (C‐19), 16.1 (C‐7′), 9.8 (C‐18) (Figure S8 and Table S1); (+)‐HR‐ESI‐MS m/z 579.3326 [M + H]⁺ (calcd for C₃₅H₄₇O₇, 579.3322) (Figure S9).

4.1.2.4. (21E)‐21‐(Pyridin‐3‐ylmethylene)‐Caudatin (1d)

Obtained as a yellow solid (14.1 mg, 28.2%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 8.68 (1H, d, J = 2.0 Hz), 8.57 (1H, d, J = 4.8 Hz), 7.89 (1H, d, J = 7.7 Hz), 7.53 (1H, d, J = 15.7 Hz), 7.29–7.32 (2H, m), 5.38 (1H, s), 5.29 (1H, s), 4.79 (1H, s), 4.72 (1H, d, J = 11.1 Hz), 4.53 (1H, s), 3.54–3.59 (1H, m), 2.90 (1H, t, J = 13.5 Hz), 2.45 (1H, s), 2.32–2.35 (2H, m), 2.23 (2H, s), 2.06–2.12 (3H, m), 1.82–1.89 (9H, m), 1.55–1.58 (2H, m), 1.38 (3H, s), 1.14 (3H, s), 1.10–1.13 (1H, m), 0.82 (6H, d, J = 6.8 Hz) (Figure S10); ¹³C NMR (100 MHz, CDCl₃): δc 198.0 (C‐20), 167.3 (C‐1′), 166.3 (C‐3′), 151.2 (C‐2″), 150.5 (C‐6″), 140.3 (C‐5), 139.3 (C‐22), 134.5 (C‐4″), 130.6 (C‐3″), 123.8 (C‐21), 123.1 (C‐5″), 118.1 (C‐6), 113.4 (C‐2′), 91.3 (C‐17), 88.1 (C‐14), 74.3 (C‐8), 72.0 (C‐12), 71.9 (C‐3), 58.9 (C‐13), 43.8 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.5 (C‐15), 33.9 (C‐7), 31.8 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.8 (C‐6′), 18.6(C‐19), 16.3 (C‐7′), 9.9 (C‐18) (Figure S11 and Table S1); (+)‐HR‐ESI‐MS m/z 580.3306 [M + H]⁺ (calcd for C₃₄H₄₆NO₇, 580.3274) (Figure S12).

4.1.2.5. (21E)‐21‐(Pyridin‐4‐ylmethylene)‐Caudatin (1e)

Obtained as a yellow solid (10.6 mg, 26.5%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 8.61 (2H, s), 7.37–7.45 (4H, m), 5.37 (1H, s), 5.27 (1H, s), 4.78 (1H, s), 4.70 (1H, d, J = 11.2 Hz), 4.45 (1H, s), 3.53–3.60 (1H, m), 2.92 (1H, t, J = 12.9 Hz), 2.39 (1H, s), 2.32–2.35 (2H, m), 2.23 (2H, s), 2.05–2.14 (3H, m), 1.93 (3H, s), 1.83–1.88 (6H, m), 1.55–1.58 (2H, m), 1.40 (3H, s), 1.14 (3H, s), 1.10–1.13 (1H, m), 0.83 (6H, d, J = 6.9 Hz) (Figure S13); ¹³C NMR (100 MHz, CDCl₃): δc 198.1 (C‐20), 167.3 (C‐1′), 166.1 (C‐3′), 150.5 (C‐2″, C‐6″), 142.1 (C‐22), 140.5 (C‐5), 139.8 (C‐4″), 125.4 (C‐3″), 122.3 (C‐21, C‐5″), 118.0 (C‐6), 113.3 (C‐2′), 91.4 (C‐17), 88.1 (C‐14), 74.3 (C‐8), 72.0 (C‐12), 71.8 (C‐3), 58.9 (C‐13), 43.8 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.5 (C‐15), 33.7 (C‐7), 31.8 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′, C‐6′), 18.7 (C‐19), 16.4 (C‐7′), 9.9 (C‐18) (Figure S14 and Table S1); (+)‐HR‐ESI‐MS m/z 580.3287 [M + H]⁺ (calcd for C₃₄H₄₆NO₇, 580.3274) (Figure S15).

4.1.2.6. (21E)‐21‐(p‐Methylbenzylidene)‐Caudatin (1f)

Obtained as a yellow solid (24.2 mg, 18.9%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.56 (1H, d, J = 15.7 Hz), 7.41 (2H, d, J = 7.5 Hz), 7.15 (2H, d, J = 7.1 Hz), 7.08 (1H, d, J = 15.7 Hz), 5.38 (1H, s), 5.29 (1H, s), 4.73–4.80 (3H, m), 3.52–3.59 (1H, m), 2.85 (1H, t, J = 12.9 Hz), 2.61 (1H, s), 2.32–2.35 (5H, m), 2.22 (2H, s), 1.83–2.08 (9H, m), 1.79 (3H, s), 1.54–1.57 (2H, m), 1.33 (3H, s), 1.15 (3H, s), 1.09–1.13 (1H, m), 0.77 (6H, d, J = 6.8 Hz) (Figure S16); ¹³C NMR (100 MHz, CDCl₃): δc 198.5 (C‐20), 167.2 (C‐1′), 166.5 (C‐3′), 144.1 (C‐22), 141.4 (C‐5), 139.9 (C‐4″), 131.8 (C‐1″), 129.6 (C‐3″, C‐5″), 128.9 (C‐2″, C‐6″), 119.5 (C‐21), 118.4 (C‐6), 113.5 (C‐2′),91.2 (C‐17), 87.8 (C‐14), 74.1 (C‐8), 72.1 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 43.7 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 36.9 (C‐10), 34.6 (C‐15), 34.4 (C‐7), 31.5 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 21.7 (─CH₃‐4″), 20.8 (C‐5′), 20.7 (C‐6′), 18.5(C‐19), 16.7 (C‐7′), 9.7 (C‐18) (Figure S17 and Table S1); (+)‐HR‐ESI‐MS m/z 593.3480 [M + H]⁺ (calcd for C₃₆H₄₉O₇, 593.3478) (Figure S18).

4.1.2.7. (21E)‐21‐(p‐Methoxybenzylidene)‐Caudatin (1g)

Obtained as a yellow solid (24.2 mg, 18.9%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.56 (1H, d, J = 15.8 Hz), 7.47 (2H, d, J = 8.1 Hz), 6.97 (1H, d, J = 15.8 Hz), 6.86 (2H, d, J = 8.2 Hz), 5.39 (1H, s), 5.30 (1H, s), 4.75–4.84 (3H, m), 3.83 (3H, s), 3.53–3.60 (1H, m), 2.83 (1H, t, J = 13.3 Hz), 2.64 (1H, s), 2.33–2.35 (2H, m), 2.23 (2H, s), 1.85–2.17 (8H, m), 1.78 (3H, s), 1.65 (2H, s), 1.55–1.58 (2H, m), 1.32 (3H, s), 1.16 (3H, s), 1.10–1.14 (1H, m), 0.78 (6H, d, J = 7.0 Hz) (Figure S19); ¹³C NMR (100 MHz, CDCl₃): δc 198.4 (C‐20), 167.2 (C‐1′), 166.6 (C‐3′), 162.0 (C‐4″), 143.9 (C‐22), 139.8 (C‐5), 130.8 (C‐2″, C‐6″), 127.4 (C‐1″), 118.5 (C‐21), 118.2 (C‐6), 114.3 (C‐3″, C‐5″), 113.6 (C‐2′), 91.1 (C‐17), 87.8 (C‐14), 74.1 (C‐8), 72.2 (C‐12), 72.1 (C‐3), 59.1 (C‐13), 55.6 (─OCH₃‐4″), 43.8 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 36.9 (C‐10), 34.7 (C‐15), 34.6 (C‐7), 31.5(C‐16), 31.1(C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.7 (C‐6′), 18.4 (C‐19), 16.1 (C‐7′), 9.7 (C‐18) (Figure S20 and Table S1); (+)‐HR‐ESI‐MS m/z 609.3424 [M + H]⁺ (calcd for C₃₆H₄₉O₈, 609.3427) (Figure S21).

4.1.2.8. (21E)‐21‐(2,4‐Dimethoxybenzylidene)‐Caudatin (1h)

Obtained as a yellow solid (16.3 mg, 25.0%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.97 (1H, d, J = 15.7 Hz), 7.52 (1H, d, J = 8.4 Hz), 6.97 (1H, d, J = 15.7 Hz), 6.46 (1H, d, J = 8.7 Hz), 6.37 (1H, s), 5.39 (1H, s), 5.28 (1H, s), 4.99 (1H, s), 4.86 (1H, s), 4.75 (1H, d, J = 9.4 Hz), 3.81 (6H, s), 3.53–3.59 (1H, m), 2.81 (1H, t, J = 12.4 Hz), 2.73 (1H, s), 2.34–2.35 (2H, m), 2.22 (2H, s), 1.87–2.11 (9H, m), 1.76 (3H, s), 1.54–1.57 (2H, m), 1.31 (3H, s), 1.15 (3H, s), 1.05–1.13 (1H, m), 0.77 (6H, d, J = 6.9 Hz) (Figure S22); ¹³C NMR (100 MHz, CDCl₃): δc 198.5 (C‐20), 166.8 (C‐1′), 166.6 (C‐3′), 163.5 (C‐4″), 160.5 (C‐2″), 139.7 (C‐22), 139.2(C‐5), 130.1 (C‐6″), 118.7 (C‐21), 117.7 (C‐6), 116.7 (C‐1″), 113.7 (C‐2′), 105.5 (C‐5″), 98.1 (C‐3″), 91.0 (C‐17), 87.7 (C‐14), 74.0 (C‐8), 72.4 (C‐12), 72.1 (C‐3), 59.1 (C‐13), 55.6 (─OCH₃‐2″), 55.5 (─OCH₃‐4″), 43.7 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.1 (C‐1), 36.9 (C‐10), 34.8 (C‐7, C‐15), 31.3 (C‐16), 31.1 (C‐2), 24.4 (C‐11), 20.6 (C‐5′), 20.5 (C‐6′), 18.4 (C‐19), 16.1 (C‐7′), 9.7 (C‐18) (Figure S23 and Table S1); (+)‐HR‐ESI‐MS m/z 639.3538 [M + H]⁺ (calcd for C₃₇H₅₁O₉, 639.3533) (Figure S24).

4.1.2.9. (21E)‐21‐(p‐Acetamidobenzylidene)‐Caudatin (1i)

Obtained as a yellow solid (16.9 mg, 28.1%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.46–7.54 (6H, m), 7.06 (1H, d, J = 15.6 Hz), 5.38 (1H, s), 5.29 (1H, s), 4.80 (1H, s), 4.74 (1H, d, J = 11.0 Hz), 3.53–3.59 (1H, m), 2.86 (1H, t, J = 12.1 Hz), 2.56 (1H, s), 2.33–2.35 (2H, m), 2.22 (2H, s), 2.19 (3H, s), 1.88–2.13 (6H, m), 1.82 (3H, s), 1.75–1.80 (2H, m), 1.54–1.57 (2H, m), 1.35 (3H, s), 1.25 (1H, s), 1.15 (3H, s), 1.09–1.12 (1H, m), 0.79 (6H, d, J = 7.0 Hz) (Figure S25); ¹³C NMR (100 MHz, CDCl₃): δc 198.4 (C‐20), 168.6 (─NH─CO─), 167.2 (C‐1′), 166.5 (C‐3′), 143.1 (C‐22), 140.3 (C‐4″), 140.0 (C‐5), 130.4 (C‐1″), 129.9 (C‐2″, C‐6″), 119.6 (C‐21), 119.5 (C‐3″, C‐5″), 118.4 (C‐6), 113.5 (C‐2′), 91.2 (C‐17), 87.9 (C‐14), 74.1 (C‐8), 72.1 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 43.7 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 36.9 (C‐10), 34.6 (C‐15), 34.3 (C‐7), 31.6 (C‐16), 31.0 (C‐2), 24.9 (─CO─CH₃), 24.4 (C‐11), 20.8 (C‐5′), 20.8(C‐6′), 18.5 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S26 and Table S1); (+)‐HR‐ESI‐MS m/z 636.3521 [M + H]⁺ (calcd for C₃₇H₅₀NO₈, 636.3536) (Figure S27).

4.1.2.10. (21E)‐21‐(p‐Formylbenzylidene)‐Caudatin (1j)

Obtained as a yellow solid (15.7 mg, 25.9%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 10.01 (1H, s), 7.86 (2H, d, J = 7.5 Hz), 7.68 (2H, d, J = 7.4 Hz), 7.56 (1H, d, J = 15.8 Hz), 7.30 (1H, d, J = 15.8 Hz), 5.38 (1H, s), 5.29 (1H, s), 4.72 (1H, d, J = 11.1 Hz), 4.49–4.57 (1H, m), 3.52–3.59 (1H, m), 2.91 (1H, t, J = 13.3 Hz), 2.42 (1H, s), 2.32–2.35 (2H, m), 2.22 (2H, s), 1.95–2.19 (9H, m), 1.88 (3H, s), 1.54–1.58 (2H, m), 1.39 (3H, s), 1.14 (3H, s), 1.10–1.13 (1H, m), 0.79 (6H, d, J = 6.8 Hz) (Figure S28); ¹³C NMR (100 MHz, CDCl₃): δc 198.2 (C‐20), 191.6 (─CHO‐4″), 167.2 (C‐1′), 166.2 (C‐3′), 141.3 (C‐22), 140.5 (C‐5), 140.3 (C‐1″), 137.4 (C‐4″), 130.1 (C‐3″, C‐5″), 129.1 (C‐2″, C‐6″), 123.9 (C‐21), 118.1 (C‐6), 113.4 (C‐2′), 91.3 (C‐17), 88.1 (C‐14), 74.3 (C‐8), 72.0 (C‐12), 71.9 (C‐3), 58.9 (C‐13), 43.8 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.5 (C‐15), 33.9 (C‐7), 31.8 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′, C‐6′), 18.6 (C‐19), 16.3 (C‐7′), 9.9 (C‐18) (Figure S29 and Table S1); (+)‐HR‐ESI‐MS m/z 607.3270 [M + H]⁺ (calcd for C₃₆H₄₇O₈, 607.3271) (Figure S30).

4.1.2.11. (21E)‐21‐(m‐Formylbenzylidene)‐Caudatin (1k)

Obtained as a yellow solid (15.7 mg, 25.9%) from caudatin (1). ¹H NMR (400 MHz, pyridine‐d₅ ): δ _H 10.15 (1H, s), 8.33 (1H, s), 8.11 (1H, d, J = 16.0 Hz), 7.95–7.99 (2H, m), 7.54 (1H, t, J = 8.1 Hz), 7.05 (1H, d, J = 16.0 Hz), 6.28 (1H, s), 5.71 (1H, s), 5.39 (1H, s), 5.22–5.26 (1H, dd, J = 11.7, 4.2 Hz), 5.02–5.05 (2H, m), 3.89–3.96 (1H, m), 3.48 (1H, t, J = 12.1 Hz), 2.66 (2H, m), 2.52–2.57 (1H, dd, J = 16.1, 4.0 Hz), 2.42 (1H, s), 2.36 (1H, d, J = 13.1 Hz), 2.27 (3H, s), 2.19–2.22 (3H, m), 2.11 (3H, s), 1.82–1.95 (4H, m), 1.42 (3H, s), 1.22–1.28 (2H, m), 0.83 (6H, d, J = 6.8 Hz) (Figure S31); ¹³C NMR (100 MHz, pyridine‐d₅ ): δc 199.6 (C‐20), 192.6 (─CHO‐3″), 166.5 (C‐1′), 165.7 (C‐3′), 140.8 (C‐22), 140.8 (C‐5),138.1 (C‐3″), 137.1 (C‐1″), 134.3 (C‐2″), 131.4 (C‐4″), 130.5 (C‐6″), 130.4 (C‐5″), 125.4 (C‐21), 119.1 (C‐6), 114.9 (C‐2′), 92.5 (C‐17), 90.0 (C‐14), 74.9 (C‐8), 73.1 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 45.1 (C‐9), 43.8 (C‐4), 39.7 (C‐4′), 38.6 (C‐1), 37.8 (C‐10), 35.4 (C‐15), 34.6 (C‐7), 33.5 (C‐16), 32.5 (C‐2), 25.6 (C‐11), 21.3 (C‐5′), 21.2 (C‐6′), 18.8 (C‐19), 16.9 (C‐7′), 11.7 (C‐18) (Figure S32 and Table S1); (+)‐HR‐ESI‐MS m/z 607.3259 [M + H]⁺ (calcd for C₃₆H₄₇O₈, 607.3271) (Figure S33).

4.1.2.12. (21E)‐21‐(p‐Cyanobenzylidene)‐Caudatin (1l)

Obtained as a yellow solid (12.3 mg, 30.3%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.60–7.66 (4H, m), 7.51 (1H, d, J = 15.7 Hz), 7.30 (1H, d, J = 15.7 Hz), 5.38 (1H, s), 5.27 (1H, s), 4.71 (2H, m), 4.43 (1H, s), 3.54–3.60 (1H, m), 2.87–2.93 (1H, t, J = 12.3 Hz), 2.32–2.36 (2H, m), 2.23 (2H, s), 1.96–2.12 (5H, m), 1.90 (3H, s), 1.75–1.83 (5H, m), 1.55–1.58 (2H, m), 1.39 (3H, s), 1.15 (3H, s), 1.10–1.13 (1H, m), 0.81 (6H, d, J = 6.8 Hz) (Figure S34); ¹³C NMR (100 MHz, CDCl₃): δc 198.1 (C‐20), 167.2 (C‐1′), 166.2 (C‐3′), 140.5 (C‐22), 140.4 (C‐5), 139.1 (C‐1″), 132.6 (C‐3″, C‐5″), 129.0 (C‐2″, C‐6″), 124.3 (C‐21), 118.5 (C‐6), 118.0 (─CN‐4″), 113.6 (C‐4″), 113.4 (C‐2′), 91.3 (C‐17), 88.1 (C‐14), 74.3 (C‐8), 72.0 (C‐12), 71.9 (C‐3), 59.0 (C‐13), 43.8 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.5 (C‐15), 33.8 (C‐7), 31.8 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′, C‐6′), 18.7 (C‐19), 16.4 (C‐7′), 9.9 (C‐18) (Figure S35 and Table S1); (+)‐HR‐ESI‐MS m/z 604.3279 [M + H]⁺ (calcd for C₃₆H₄₆NO₇, 604.3274) (Figure S36).

4.1.2.13. (21E)‐21‐(p‐Nitrobenzylidene)‐Caudatin (1m)

Obtained as a yellow solid (15.6 mg, 32.6%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 8.21 (2H, d, J = 7.8 Hz), 7.67 (2H, d, J = 8.3 Hz), 7.54 (1H, d, J = 15.8 Hz), 7.33 (1H, d, J = 15.8 Hz), 5.38 (1H, s), 5.28 (1H, s), 4.69–4.71 (2H, m), 4.38 (1H, s), 3.53–3.59 (1H, m), 2.90–2.96 (1H, t, J = 11.6 Hz), 2.33–2.35 (2H, m), 2.23 (2H, s), 1.95–2.13 (4H, m), 1.92 (3H, s), 1.80–1.88 (6H, m), 1.55–1.58 (2H, m), 1.40 (3H, s), 1.14 (3H, s), 1.09–1.13 (1H, m), 0.81 (6H, d, J = 6.7 Hz) (Figure S37); ¹³C NMR (100 MHz, CDCl₃): δc 198.0 (C‐20), 167.2 (C‐1′), 166.1 (C‐3′), 148.6 (C‐4″), 141.0 (C‐22), 140.5 (C‐5), 139.8 (C‐1″), 129.2 (C‐2″, C‐6″), 125.1 (C‐21), 124.1 (C‐3″, C‐5″), 118.0 (C‐6), 113.3 (C‐2′), 91.4 (C‐17), 88.1 (C‐14), 74.4 (C‐8), 72.0 (C‐12), 71.8 (C‐3), 58.9 (C‐13), 43.8 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.4 (C‐15), 33.6 (C‐7), 31.9 (C‐16), 30.9 (C‐2), 24.4 (C‐11), 20.8 (C‐5′, C‐6′), 18.7 (C‐19), 16.4 (C‐7′), 9.9 (C‐18) (Figure S38 and Table S2); (+)‐HR‐ESI‐MS m/z 624.3159 [M + H]⁺ (calcd for C₃₅H₄₆NO₉, 624.3173) (Figure S39).

4.1.2.14. (21E)‐21‐(p‐Trifluoromethylbenzylidene)‐Caudatin (1n)

Obtained as a yellow solid (23.1 mg, 37.7%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.58–7.63 (4H, m), 7.54 (1H, d, J = 15.6 Hz), 7.24 (1H, d, J = 15.6 Hz), 5.37 (1H, s), 5.27 (1H, s), 4.71–4.73 (2H, m), 4.52 (1H, s), 3.51–3.60 (1H, m), 2.86–2.92 (1H, t, J = 12.4 Hz), 2.43 (1H, s), 2.32–2.34 (2H, m), 2.22 (2H, s), 1.89–2.11 (5H, m), 1.86 (3H, s), 1.79–1.82 (4H, m), 1.54–1.57 (2H, m), 1.37 (3H, s), 1.14 (3H, s), 1.09–1.12 (1H, m), 0.79 (6H, d, J = 6.7 Hz) (Figure S40); ¹³C NMR (100 MHz, CDCl₃): δc 198.3 (C‐20), 167.3 (C‐1′), 166.3 (C‐3′), 141.3 (C‐22), 140.3 (C‐5), 138.1 (C‐1″), 132.1 (dd, J = 65.2, 32.5 Hz, C‐4″), 128.8 (C‐2″, C‐6″), 123.9 (dd, J = 272.3 Hz, ─CF₃‐4″), 125.8 (q, J = 7.7, 3.8 Hz, C‐3″, C‐5″), 123.3 (C‐21), 118.1 (C‐6), 113.4 (C‐2′), 91.3 (C‐17), 88.0 (C‐14), 74.3 (C‐8), 72.0 (C‐12), 71.9 (C‐3), 59.0 (C‐13), 43.8 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.5 (C‐15), 34.0 (C‐f7), 31.7 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.7 (C‐6′), 18.6 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S41 and Table S2); (+)‐HR‐ESI‐MS m/z 647.3184 [M + H]⁺ (calcd for C₃₆H₄₆O₇F₃, 647.3196) (Figure S42).

4.1.2.15. (21E)‐21‐(p‐Fluorobenzylidene)‐Caudatin (1o)

Obtained as a yellow solid (25.0 mg, 41.1%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.50–7.55 (3H, m), 7.02–7.08 (3H, m), 5.38 (1H, s), 5.29 (1H, s), 4.72–4.76 (2H, m), 3.52–3.60 (1H, m), 2.81–2.89 (1H, m), 2.55 (1H, s), 2.32–2.35 (2H, m), 2.22 (2H, m), 1.88–2.19 (7H, m), 1.83 (3H, s), 1.77–1.80 (3H, m), 1.54–1.58 (2H, m), 1.34 (3H, s), 1.15 (3H, s), 1.09–1.12 (1H, m), 0.78 (6H, d, J = 6.8 Hz) (Figure S43); ¹³C NMR (100 MHz, CDCl₃): δc 198.3 (C‐20), 167.2 (C‐1′), 166.4 (C‐3′), 164.3 (d, J = 252.1 Hz, C‐4″), 142.4 (C‐22), 140.0 (C‐5), 130.9 (d, J = 3.3 Hz C‐1″), 130.8 (C‐2″), 130.7 (C‐6″), 120.5 (C‐21), 118.3 (C‐6), 116.2 (C‐3″), 115.9 (C‐5″), 113.5 (C‐2′), 91.2 (C‐17), 87.9 (C‐14), 74.1 (C‐8), 72.1 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 43.8 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.6 (C‐15), 34.3 (C‐7), 31.6 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.7 (C‐6′), 18.5 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S44 and Table S2); (+)‐HR‐ESI‐MS m/z 597.3237 [M + H]⁺ (calcd for C₃₅H₄₆O₇F, 597.3228) (Figure S45).

4.1.2.16. (21E)‐21‐(m‐Fluorobenzylidene)‐CAUDATIN (1p)

Obtained as a yellow solid (26.0 mg, 42.8%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.50 (1H, d, J = 15.6 Hz), 7.27–7.35 (2H, m), 7.23 (1H, d, J = 10.0 Hz), 7.15 (1H, d, J = 15.6 Hz), 7.06 (1H, t, J = 8.3 Hz), 5.38 (1H, s), 5.29 (1H, s), 4.70–4.73 (2H, m), 4.60 (1H, s), 3.52–3.60 (1H, m), 2.84–2.92 (1H, m), 2.49 (1H, s), 2.32–2.35 (2H, m), 2.22 (2H, s), 1.90–2.17 (5H, m), 1.87 (3H, s), 1.74–1.84 (4H, m), 1.54–1.57 (2H, m), 1.36 (3H, s), 1.14 (3H, s), 1.09–1.13 (1H, m), 0.80 (6H, d, J = 6.6 Hz) (Figure S46); ¹³C NMR (100 MHz, CDCl₃): δc 198.3 (C‐20), 167.3 (C‐1′), 166.3 (C‐3′), 163.1 (d, J = 246.8 Hz, C‐3″), 142.1 (C‐22), 140.2 (C‐5), 137.0 (d, J = 7.8 Hz, C‐1″), 130.5 (d, J = 8.2 Hz, C‐5″), 124.8 (d, J = 2.9 Hz, C‐6″), 122.1 (C‐21), 118.2 (C‐6), 117.5 (d, J = 21.2 Hz,C‐4″), 114.9 (d, J = 21.8 Hz,C‐2″), 113.4 (C‐2′), 91.3 (C‐17), 88.0 (C‐14), 74.2 (C‐8), 72.0 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 43.8 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.6 (C‐15), 34.1 (C‐7), 31.6 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.7 (C‐6′), 18.6 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S47 and Table S2); (+)‐HR‐ESI‐MS m/z 597.3245 [M + H]⁺ (calcd for C₃₅H₄₆O₇F, 597.3228) (Figure S48).

4.1.2.17. (21E)‐21‐(o‐Fluorobenzylidene)‐Caudatin (1q)

Obtained as a yellow solid (45.4 mg, 74.7%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.75 (1H, d, J = 15.8 Hz), 7.60 (1H, t, J = 7.5 Hz), 7.34 (1H, d, J = 7.5 Hz), 7.23 (1H, d, J = 15.8 Hz), 7.13 (1H, t, J = 7.6 Hz), 7.05 (1H, dd, J = 9.5, 7.5 Hz), 5.38 (1H, s), 5.30 (1H, s), 4.63–4.73 (2H, m), 4.63 (1H, s), 3.52–3.60 (1H, m), 2.85–2.92 (1H, m), 2.51 (1H, s), 2.32–2.35 (2H, m), 2.22 (2H, s), 1.87–2.18 (7H, m), 1.83 (3H, s), 1.76–1.80 (2H, m), 1.54–1.57 (2H, m), 1.36 (3H, s), 1.14 (3H, s), 1.10–1.14 (1H, m), 0.80 (6H, d, J = 6.7 Hz) (Figure S49); ¹³C NMR (100 MHz, CDCl₃): δc 198.4 (C‐20), 167.3 (C‐1′), 166.3 (C‐3′), 161.8 (d, J = 254.8 Hz, C‐2″), 140.1 (C‐5), 135.7 (d, J = 4.0 Hz, C‐22), 132.2 (d, J = 8.7 Hz, C‐4″), 129.0 (d, J = 2.7 Hz, C‐6″), 124.5 (d, J = 3.5 Hz,C‐5″), 122.8 (d, J = 6.0 Hz, C‐21), 122.7 (C‐1″), 118.3 (C‐6), 116.2 (d, J = 21.8 Hz,C‐3″), 113.4 (C‐2′), 91.2 (C‐17), 88.0 (C‐14), 74.2 (C‐8), 72.0 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 43.8 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.6 (C‐15), 34.2 (C‐7), 31.6 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.7 (C‐5′), 20.6 (C‐6′), 18.5 (C‐19), 16.1 (C‐7′), 9.8 (C‐18) (Figure S50 and Table S2); (+)‐HR‐ESI‐MS m/z 597.3234 [M + H]⁺ (calcd for C₃₅H₄₆O₇F, 597.3228) (Figure S51).

4.1.2.18. (21E)‐21‐(3,4‐Difluorobenzylidene)‐Caudatin (1r)

Obtained as a yellow solid (25.8 mg, 41.1%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.44 (1H, d, J = 15.6 Hz), 7.36 (1H, t, J = 9.3 Hz), 7.24 (1H, m), 7.11–7.17 (1H, dd, J = 9.0, 8.1 Hz), 7.08 (1H, d, J = 15.6 Hz), 5.38 (1H, s), 5.29 (1H, s), 4.70–4.72 (2H, m), 4.56 (1H, s), 3.52–3.60 (1H, m), 2.83–2.91 (1H, m), 2.46 (1H, s), 2.32–2.35 (2H, m), 2.22 (2H, s), 1.93–2.16 (5H, m), 1.90 (3H, s), 1.79–1.87 (4H, m), 1.54–1.57 (2H, m), 1.36 (3H, s), 1.14 (3H, s), 1.09–1.12 (1H, m), 0.82 (6H, d, J = 6.9 Hz) (Figure S52); ¹³C NMR (100 MHz, CDCl₃): δc 198.2 (C‐20), 167.2 (C‐1′), 166.3 (C‐3′), 152.4 (dd, J = 1113.4, 113.1 Hz, C‐4″), 149.9 (dd, J = 1119.1, 123.0 Hz, C‐3″), 141.0 (C‐22), 140.2 (C‐5), 132.0 (q, J = 50.7, 49.3 Hz, C‐1″), 125.6 (dd, J = 46.6, 43.5 Hz, C‐6″), 122.0 (C‐21), 118.2 (C‐6), 117.8 (d, J = 17.9 Hz, C‐5″), 116.9 (d, J = 17.6 Hz, C‐2″), 113.4 (C‐2′), 91.3 (C‐17), 88.0 (C‐14), 74.2 (C‐8), 72.0 (C‐12), 71.9 (C‐3), 58.9 (C‐13), 43.7 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.5 (C‐15), 34.0 (C‐7), 31.7 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.8 (C‐6′), 18.6 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S53 and Table S2); (+)‐HR‐ESI‐MS m/z 615.3131 [M + H]⁺ (calcd for C₃₅H₄₅O₇F₂, 615.3133) (Figure S54).

4.1.2.19. (21E)‐21‐(2,4‐Difluorobenzylidene)‐Caudatin (1s)

Obtained as a yellow solid (12.9 mg, 20.6%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.68 (1H, d, J = 15.8 Hz), 7.58–7.63 (1H, dd, J = 8.5, 7.8 Hz), 7.18 (1H, d, J = 15.8 Hz), 6.80–6.91 (2H, m), 5.38 (1H, s), 5.30 (1H, s), 4.71–4.73 (2H, m), 4.56 (1H, s), 3.52–3.60 (1H, m), 2.84–2.92 (1H, m), 2.46 (1H, s), 2.32–2.35 (2H, m), 2.22 (2H, s), 1.90–2.16 (7H, m), 1.87 (3H, s), 1.80–1.84 (2H, m), 1.54–1.58 (2H, m), 1.36 (3H, s), 1.15 (3H, s), 1.10–1.13 (1H, m), 0.82 (6H, d, J = 6.8 Hz) (Figure S55); ¹³C NMR (100 MHz, CDCl₃): δc 198.2 (C‐20), 167.3 (C‐1′), 166.3 (C‐3′), 164.1 (dd, J = 166.5, 52.4 Hz, C‐4″), 161.0 (dd, J = 113.2, 4.2 Hz, C‐2″), 140.8 (C‐22), 140.2 (C‐5), 130.2 (dd, J = 8.4, 2.7 Hz, C‐6″), 122.6 (d, J = 8.4 Hz, C‐21), 119.5 (dd, J = 11.3, 4.0 Hz, C‐1″), 118.2 (C‐6), 113.4 (C‐2′), 112.1 (dd, J = 20.3, 3.9 Hz, C‐5″), 104.6 (q, J = 6.0, 4.4 Hz, C‐3″), 91.2 (C‐17), 88.0 (C‐14), 74.2 (C‐8), 72.4 (C‐12), 72.0 (C‐3), 58.9 (C‐13), 43.8 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.6 (C‐15), 34.0 (C‐7), 31.7 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.7 (C‐5′, C‐6′), 18.6 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S56 and Table S2) (+)‐HR‐ESI‐MS m/z 615.3123 [M + H]⁺ (calcd for C₃₅H₄₅O₇F₂, 615.3133) (Figure S57).

4.1.2.20. (21E)‐21‐(3,5‐Difluorobenzylidene)‐Caudatin (1t)

Obtained as a yellow solid (34.7 mg, 56.3%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.42 (1H, d, J = 15.7 Hz), 7.16 (1H, d, J = 15.7 Hz), 7.03 (2H, d, J = 8.5 Hz), 6.82 (1H, t, J = 8.6 Hz), 5.38 (1H, s), 5.29 (1H, s), 4.68–4.72 (2H, m), 4.47 (1H, s), 3.53–3.60 (1H, m), 2.85–2.93 (1H, m), 2.39 (1H, s), 2.29–2.35 (2H, m), 2.22 (2H, s), 1.97–2.18 (4H, m), 1.94 (3H, s), 1.75–1.91 (5H, m), 1.54–1.58 (2H, m), 1.37 (3H, s), 1.14 (3H, s), 1.10–1.13 (1H, m), 0.84 (6H, d, J = 6.6 Hz) (Figure S58); ¹³C NMR (100 MHz, CDCl₃): δc 198.2 (C‐20), 167.4 (C‐1′), 166.2 (C‐3′), 164.5 (d, J = 12.4 Hz, C‐3″), 162.0 (d, J = 12.9 Hz, C‐5″), 140.5 (C‐22), 140.4 (C‐5), 138.1 (t, J = 9.5 Hz, C‐1″), 123.5 (C‐21), 118.1 (C‐6), 113.3 (C‐2′), 111.2 (m, J = 18.8, 6.9 Hz, C‐2″, C‐6″), 105.7 (t, J = 25.5 Hz, C‐4″), 91.3 (C‐17), 88.0 (C‐14), 74.3 (C‐8), 72.0 (C‐12), 71.8 (C‐3), 58.9 (C‐13), 43.8 (C‐9), 42.1 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.5 (C‐15), 33.8 (C‐7), 31.7 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.8 (C‐6′), 18.6 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S59 and Table S2); (+)‐HR‐ESI‐MS m/z 615.3124 [M + H]⁺ (calcd for C₃₅H₄₅O₇F₂, 615.3133) (Figure S60).

4.1.2.21. (21E)‐21‐(3,4,5‐Trifluorobenzylidene)‐Caudatin (1u)

Obtained as a yellow solid (28.7 mg, 45.4%) from caudatin (1). ¹H NMR (400 MHz, pyridine‐d₅ ): δ _H 7.98 (1H, d, J = 15.8 Hz), 7.74–7.81 (1H, m), 7.50 (1H, d, J = 8.7 Hz), 7.04 (1H, d, J = 15.8 Hz), 6.28 (1H, s), 5.72 (1H, s), 5.39 (1H, s), 5.23 (1H, d, J = 6.8 Hz), 5.05 (1H, s), 4.20–4.26 (1H, m), 3.89–3.96 (1H, m), 3.43–3.50 (1H, m), 2.67–2.71 (2H, m), 2.51–2.57 (1H, m), 2.34–2.42 (2H, m), 2.19–2.27 (6H, m), 2.09–2.11 (3H, m), 1.82–1.94 (3H, m), 1.41 (3H, s), 1.21–1.32 (3H, m), 0.86 (6H, d, J = 6.7 Hz) (Figure S61); ¹³C NMR (100 MHz, pyridine‐d₅ ): δc 199.5 (d, J = 6.4 Hz, C‐20), 166.5 (d, J = 4.2 Hz, C‐1′), 165.8 (d, J = 11.7 Hz, C‐3′), 158.0 (d, J = 5.9 Hz, C‐3″), 155.6 (d, J = 6.4 Hz, C‐5″), 140.8 (C‐5), 139.9 (C‐4″), 139.0 (C‐22), 126.3 (C‐1″), 125.1 (C‐21), 119.1 (C‐6), 114.9 (d, J = 7.6 Hz, C‐2′), 113.4 (q, J = 16.2, 5.4 Hz, C‐2″), 113.1 (q, J = 16.9, 6.5 Hz, C‐6″), 92.5 (C‐17), 90.0 (C‐14), 74.9 (C‐8), 73.1 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 45.1 (C‐9), 43.8 (C‐4), 39.7 (C‐4′), 38.6 (C‐1), 37.9 (C‐10), 35.4 (C‐15), 34.7 (C‐7), 33.6 (C‐16), 32.5 (C‐2), 25.6 (C‐11), 21.2 (C‐5′), 21.2 (C‐6′), 18.8 (C‐19), 16.9 (C‐7′), 11.8 (C‐18) (Figure S62 and Table S2); (+)‐HR‐ESI‐MS m/z 633.3022 [M + H]⁺ (calcd for C₃₅H₄₄O₇F₃, 633.3039) (Figure S63).

4.1.2.22. (21E)‐21‐(p‐Chlorobenzylidene)‐Caudatin (1v)

Obtained as a yellow solid (14.3 mg, 31.3%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.51 (1H, d, J = 15.7 Hz), 7.45 (2H, d, J = 8.2 Hz), 7.33 (2H, d, J = 7.8 Hz), 7.12 (1H, d, J = 15.7 Hz), 5.39 (1H, s), 5.29 (1H, s), 4.74 (2H, m), 4.63 (1H, s), 3.53–3.60 (1H, m), 2.83–2.89 (1H, t, J = 12.5 Hz), 2.50 (1H, s), 2.33–2.35 (2H, m), 2.23 (2H, s), 1.88–2.18 (7H, m), 1.85 (3H, s), 1.69 (2H, m), 1.55–1.58 (2H, m), 1.35 (3H, s), 1.15 (3H, s), 1.10–1.13 (1H, m), 0.80 (6H, d, J = 6.8 Hz) (Figure S64); ¹³C NMR (100 MHz, CDCl₃): δc 198.3 (C‐20), 167.3 (C‐1′), 166.4 (C‐3′), 142.1 (C‐22), 140.1 (C‐5), 136.7 (C‐4″), 133.2 (C‐1″), 130.0 (C‐2″, C‐6″), 129.2 (C‐3″,C‐5″), 121.3 (C‐21), 118.3 (C‐6), 113.5 (C‐2′), 91.2 (C‐17), 87.9 (C‐14), 74.2 (C‐8), 72.1 (C‐12), 72.0 (C‐3), 59.0 (C‐13), 43.8 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.6 (C‐15), 34.2 (C‐7), 31.6 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.7 (C‐6′), 18.5 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S65 and Table S2); (+)‐HR‐ESI‐MS m/z 613.2937 [M + H]⁺ (calcd for C₃₅H₄₆O₇Cl, 613.2932) (Figure S66).

4.1.2.23. (21E)‐21‐(p‐Bromobenzylidene)‐Caudatin (1w)

Obtained as a yellow solid (23.2 mg, 34.7%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 7.47–7.51 (3H, m), 7.38 (2H, d, J = 8.0 Hz), 7.14 (1H, d, J = 15.7 Hz), 5.38 (1H, s), 5.28 (1H, s), 4.71–4.74 (2H, m), 4.62 (1H, s), 3.52–3.60 (1H, m), 2.83–2.90 (1H, m), 2.50 (1H, s), 2.32–2.35 (2H, m), 2.22 (2H, s), 1.88–2.17 (6H, m), 1.85 (3H, s), 1.75–1.80 (3H, m), 1.54–1.58 (2H, m), 1.35 (3H, s), 1.15 (3H, s), 1.10–1.13 (1H, m), 0.80 (6H, d, J = 6.9 Hz) (Figure S67); ¹³C NMR (100 MHz, CDCl₃): δc 198.3 (C‐20), 167.3 (C‐1′), 166.4 (C‐3′), 142.2 (C‐22), 140.1 (C‐5), 133.6 (C‐1″), 132.1 (C‐3″, C‐5″), 130.2 (C‐2″, C‐6″), 125.0 (C‐4″), 121.4 (C‐21), 118.3 (C‐6), 113.5 (C‐2′), 91.2 (C‐17), 87.9 (C‐14), 74.2 (C‐8), 72.0 (C‐3, C‐12), 59.0 (C‐13), 43.7 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 38.2 (C‐1), 37.0 (C‐10), 34.6 (C‐15), 34.2 (C‐7), 31.6 (C‐16), 31.0 (C‐2), 24.4 (C‐11), 20.8 (C‐5′), 20.7 (C‐6′), 18.5 (C‐19), 16.2 (C‐7′), 9.8 (C‐18) (Figure S68 and Table S2); (+)‐HR‐ESI‐MS m/z 657.2431 [M + H]⁺ (calcd for C₃₅H₄₆O₇Br, 657.2427) (Figure S69).

4.1.3. General Procedure for the Synthesis of Caudatin Derivatives With Quinolyl Substituents (2a–2h)

To a stirred solution of caudatin (1, 1.0 equiv.) in anhydrous EtOH (10 mL) was added t‐BuOK (2.5 equiv.) and 2‐aminoaromatic aldehydes with different substituents (3.5 equiv.), and the reaction mixture was stirred to react for 3 h at 100°C until no starting material was observed by TLC. After completion of the reaction, the mixture was concentrated under reduced pressure, diluted with EtOAc, and washed successively with 1 M HCl, saturated NaHCO₃, and water. The resulting organic layer was dried over anhydrous Na₂SO₄ and then concentrated under reduced pressure to afford the crude product. The crude product was purified by semi‐preparative RP‐HPLC (70%–80% MeOH–H₂O) to obtain the target quinolyl derivatives (2a–2h).

4.1.3.1. 21‐(Quinolin‐2‐yl)‐Caudatin (2a)

Obtained as a yellow solid (16.4 mg, 28.5%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 8.05 (1H, d, J = 8.6 Hz), 7.95 (1H, d, J = 8.5 Hz), 7.69 (2H, d, J = 7.8 Hz), 7.46–7.53 (2H, m), 5.42 (1H, s), 4.86–4.90 (1H, dd, J = 11.4, 4.3 Hz), 4.45 (1H, s), 3.53–3.61 (1H, m), 3.07 (1H, m), 2.84 (1H, s), 2.34–2.36 (2H, m), 2.28 (2H, m), 2.14–2.24 (3H, m), 1.73–1.88 (8H, m), 1.70 (3H, s), 1.50–1.60 (2H, m), 1.32 (3H, s), 1.25–1.30 (1H, m), 1.14 (3H, s), 0.66 (6H, d, J = 6.8 Hz) (Figure S70); ¹³C NMR (100 MHz, CDCl₃): δc 166.3 (C‐1′), 164.8 (C‐3′), 160.3 (C‐2″), 146.1 (C‐10″), 139.5 (C‐5), 136.1 (C‐4″), 129.7 (C‐8″), 129.2 (C‐9″), 127.3 (C‐5″), 127.1 (C‐6″), 126.6 (C‐7″), 118.9 (C‐6), 118.6 (C‐3″), 113.8 (C‐2′), 87.9 (C‐14, C‐17), 74.1 (C‐8), 72.8 (C‐12), 72.1 (C‐3), 58.3 (C‐13), 43.6 (C‐9), 42.3 (C‐4), 38.9 (C‐4′), 37.8 (C‐1), 36.9 (C‐10), 34.7 (C‐15), 34.7 (C‐7), 33.3 (C‐16), 31.1 (C‐2), 24.6 (C‐11), 20.8 (C‐5′), 20.5 (C‐6′), 18.4 (C‐19), 16.3 (C‐7′), 9.6 (C‐18) (Figure S71 and Table S3); (+)‐HR‐ESI‐MS m/z 576.3345 [M + H]⁺ (calcd for C₃₅H₄₆NO₆, 576.3325) (Figure S72).

4.1.3.2. 21‐(Pyrido[2,3‐b]pyrazin‐2‐yl)‐Caudatin (2b)

Obtained as a yellow solid (12.0 mg, 22.3%) from caudatin (1). ¹H NMR (400 MHz, Pyridine‐d₅ ): δ _H 9.18 (1H, s), 8.29–8.35 (2H, m), 8.21 (1H, d, J = 8.1 Hz), 7.40–7.43 (1H, m), 7.30 (1H, s), 6.47 (1H, d, J = 15.8 Hz), 6.30 (1H, s), 5.42–5.47 (2H, m), 4.87 (1H, m), 4.51 (1H, s), 4.30 (1H, s), 3.99 (1H, m), 2.69 (2H, m), 2.55–2.60 (1H, m), 2.42–2.47 (2H, m), 2.21–2.31 (3H, m), 2.11–2.13 (1H, m), 1.97 (3H, s), 1.83 (3H, s), 1.71–1.75 (1H, m), 1.40 (3H, s), 0.67 (6H, d, J = 6.8 Hz) (Figure S73); ¹³C NMR (100 MHz, Pyridine‐d ₅): δc 167.6 (C‐1′), 165.5 (C‐3′), 164.2 (C‐2″), 156.1 (C‐10″), 153.9 (C‐8″), 140.7 (C‐5), 137.4 (C‐6″), 137.1 (C‐4″), 122.8 (C‐5″), 122.7 (C‐7″), 122.5 (C‐3″), 119.2 (C‐6), 113.8 (C‐2′), 90.3 (C‐17), 89.9 (C‐14), 74.9 (C‐8), 73.4 (C‐12), 72.0 (C‐3), 58.8 (C‐13), 44.8 (C‐9), 43.9 (C‐4), 39.8 (C‐4′), 38.0 (C‐1), 37.8 (C‐10), 35.4 (C‐15), 35.0 (C‐7), 34.9 (C‐16), 32.5 (C‐2), 25.4 (C‐11), 21.3 (C‐5′), 21.0 (C‐6′), 18.8 (C‐19), 16.8 (C‐7′), 10.9 (C‐18) (Figure S74 and Table S3); (+)‐HR‐ESI‐MS m/z 577.3301 [M + H]⁺ (calcd for C₃₄H₄₅N₂O₆, 577.3278) (Figure S75).

4.1.3.3. 21‐(5‐Fluoroquinolin‐2‐yl)‐Caudatin (2c)

Obtained as a yellow solid (14.2 mg, 23.1%) from caudatin (1).¹H NMR (400 MHz, CDCl₃): δ _H 8.04 (1H, d, J = 8.1 Hz), 7.92 (1H, d, J = 8.2 Hz), 7.59 (1H, d, J = 8.7 Hz), 7.44 (1H, t, J = 8.0 Hz), 7.30 (1H, d, J = 8.8 Hz), 5.42 (1H, s), 4.86 (1H, dd, J = 11.1, 4.0 Hz), 4.42 (1H, s), 3.54–3.60 (1H, m), 3.16 (1H, m), 2.70 (1H, s), 2.33–2.36 (2H, m), 2.28 (2H, m), 2.15–2.23 (3H, m), 1.80–1.89 (5H, m), 1.72 (3H, s), 1.54–1.61 (5H, m), 1.32 (3H, s), 1.25–1.28 (1H, m), 1.14 (3H, s), 0.70 (6H, d, J = 6.8 Hz) (Figure S76); ¹³C NMR (100 MHz, CDCl₃): δc 166.0 (C‐1′), 165.0 (C‐3′), 161.0 (d, J = 168.4 Hz, C‐7″), 159.3 (C‐2″), 143.4 (d, J = 5.3 Hz, C‐10″), 139.8 (C‐5), 135.4 (d, J = 4.6 Hz, C‐4″), 131.9 (d, J = 3.4 Hz, C‐9″), 127.8 (d, J = 9.4 Hz, C‐5″), 119.9 (C‐6), 119.7 (C‐3″), 118.7 (d, J = 2.0 Hz, C‐8″), 113.5 (C‐2′), 110.3 (d, J = 21.7 Hz, C‐6″), 87.9 (C‐14, C‐17), 74.2 (C‐8), 72.6 (C‐12), 72.1 (C‐3), 58.2 (C‐13), 43.5 (C‐9), 42.3 (C‐4), 38.9 (C‐4′), 37.8 (C‐1), 36.9 (C‐10), 34.4 (C‐15), 34.2 (C‐7), 33.4 (C‐16), 31.1 (C‐2), 24.6 (C‐11), 20.7 (C‐5′), 20.6 (C‐6′), 18.4 (C‐19), 16.4 (C‐7′), 9.6 (C‐18) (Figure S77 and Table S3); (+)‐HR‐ESI‐MS m/z 594.3245 [M + H]⁺ (calcd for C₃₅H₄₅NO₆F, 594.3231) (Figure S78).

4.1.3.4. 21‐(6‐Chloroquinolin‐2‐Yl)‐Caudatin (2d)

Obtained as a yellow solid (10.0 mg, 16.1%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 8.38 (1H, d, J = 8.5 Hz), 7.97 (1H, d, J = 8.2 Hz), 7.68 (1H, d, J = 9.0 Hz), 7.53–7.60 (2H, m), 5.42 (1H, s), 4.86–4.89 (1H, m), 4.42 (1H, s), 3.52–3.61 (1H, m), 3.17 (1H, m), 2.71 (1H, s), 2.33–2.36 (2H, m), 2.28 (2H, m), 2.16–2.22 (3H, m), 1.80–1.89 (6H, m), 1.73 (3H, s), 1.54–1.61 (4H, m), 1.33 (3H, s), 1.25–1.29 (1H, m), 1.14 (3H, s), 0.67 (6H, d, J = 6.8 Hz) (Figure S79); ¹³C NMR (100 MHz, CDCl₃): δc 166.0 (C‐1′), 165.4 (C‐3′), 161.6 (C‐2″), 147.0 (C‐10″), 139.8 (C‐5), 132.9 (C‐6″), 131.2 (C‐4″), 129.3 (C‐8″), 128.6 (C‐9″), 126.5 (C‐5″), 125.4 (C‐7″), 119.9 (C‐6), 118.7 (C‐3″), 113.2 (C‐2′), 88.0 (C‐14, C‐17), 74.2 (C‐8), 72.5 (C‐12), 72.1 (C‐3), 58.4 (C‐13), 43.5 (C‐9), 42.3 (C‐4), 38.9 (C‐4′), 37.8 (C‐1), 36.9 (C‐10), 34.6 (C‐15, C‐7), 33.4 (C‐16), 31.1 (C‐2), 24.6 (C‐11), 20.8 (C‐5′), 20.5 (C‐6′), 18.4 (C‐19), 16.6 (C‐7′), 9.6 (C‐18) (Figure S80 and Table S3); (+)‐HR‐ESI‐MS m/z 610.2939 [M + H]⁺ (calcd for C₃₅H₄₅NO₆Cl, 610.2935) (Figure S81).

4.1.3.5. 21‐(4‐Chloroquinolin‐2‐yl)‐Caudatin (2e)

Obtained as a yellow solid (11.2 mg, 14.3%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 8.05 (1H, d, J = 8.1 Hz), 7.95 (1H, d, J = 8.1 Hz), 7.59–7.63 (2H,m), 7.43 (1H, d, J = 8.1 Hz), 5.41 (1H, s), 4.86–4.89 (1H, m), 4.41 (1H, s), 3.54–3.60 (1H, m), 3.19 (1H, m), 2.66 (1H, s), 2.33–2.36 (2H, m), 2.28 (2H, m), 2.16–2.20 (3H, m), 1.80–1.89 (5H, m), 1.75 (3H, s), 1.51–1.61 (5H, m), 1.32 (3H, s), 1.25–1.29 (1H, m), 1.14 (3H, s), 0.68 (6H, d, J = 6.8 Hz) (Figure S82); ¹³C NMR (100 MHz, CDCl₃): δc 166.0 (C‐1′), 165.2 (C‐3′), 162.0 (C‐2″), 146.7 (C‐10″), 139.8 (C‐5), 135.7 (C‐8″), 135.4 (C‐4″), 128.5 (C‐6″), 128.5 (C‐5″), 127.6 (C‐7″), 125.5 (C‐9″), 119.3 (C‐6), 118.6 (C‐3″), 113.4 (C‐2′), 88.0 (C‐14, C‐17), 74.3 (C‐8), 72.5 (C‐12), 72.1 (C‐3), 58.3 (C‐13), 43.6 (C‐9), 42.3 (C‐4), 38.9 (C‐4′), 37.8 (C‐1), 36.9 (C‐10), 34.6 (C‐7, C‐15), 33.5 (C‐16), 31.1 (C‐2), 24.5 (C‐11), 20.8 (C‐5′), 20.6 (C‐6′), 18.5 (C‐19), 16.3 (C‐7′), 9.5 (C‐18) (Figure S83 and Table S3); (+)‐HR‐ESI‐MS m/z 610.2933 [M + H]⁺ (calcd for C₃₅H₄₅NO₆Cl, 610.2935) (Figure S84).

4.1.3.6. 21‐(5‐Bromoquinolin‐2‐yl)‐Caudatin (2f)

Obtained as a yellow solid (24.2 mg, 40.1%) from caudatin ¹H NMR (400 MHz, CDCl₃): δ _H 7.84–7.89 (3H, m), 7.72 (1H, d, J = 9.0 Hz), 7.62 (1H, d, J = 8.8 Hz), 5.41 (1H, s), 4.83–4.86 (1H, dd, J = 11.4, 3.6 Hz), 4.38 (1H, s), 3.52–3.60 (1H, m), 3.22 (1H, m), 2.64 (1H, s), 2.33–2.36 (2H, m), 2.28 (2H, m), 2.15–2.20 (3H, m), 1.78–1.88 (6H, m), 1.70 (3H, s), 1.50–1.61 (4H, m), 1.32 (3H, s), 1.25 (1H, m), 1.13 (3H, s), 0.70 (6H, d, J = 6.9 Hz) (Figure S85); ¹³C NMR (100 MHz, CDCl₃): δc 165.9 (C‐1′), 165.1 (C‐3′), 161.3 (C‐2″), 144.9 (C‐10″), 139.9 (C‐5), 134.8 (C‐4″), 132.9 (C‐8″), 131.2 (C‐6″), 129.3 (C‐5″), 128.3 (C‐9″), 120.3 (C‐3″), 119.9 (C‐6), 118.5 (C‐7″), 113.3 (C‐2′), 88.0 (C‐14, C‐17), 74.2 (C‐8), 72.4 (C‐12), 72.0 (C‐3), 58.2 (C‐13), 43.5 (C‐9), 42.2 (C‐4), 38.8 (C‐4′), 37.8 (C‐1), 36.9 (C‐10), 34.6 (C‐7, C‐15), 33.4 (C‐16), 31.0 (C‐2), 24.5 (C‐11), 20.7 (C‐5′), 20.5 (C‐6′), 18.4 (C‐19), 16.4 (C‐7′), 9.5 (C‐18) (Figure S86 and Table S3); (+)‐HR‐ESI‐MS m/z 654.2411 [M + H]⁺ (calcd for C₃₅H₄₅NO₆Br, 654.2430) (Figure S87).

4.1.3.7. 21‐(5‐Bromopyrido[2,3‐b]pyrazin‐2‐yl)‐Caudatin (2g)

Obtained as a yellow solid (24.0 mg, 34.3%, Table S4) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 9.04 (1H, s), 8.22 (1H, s), 7.97 (1H, d, J = 8.3 Hz), 7.79 (1H, d, J = 8.7 Hz), 5.40 (1H, s), 4.90 (1H, dd, J = 11.0, 3.9 Hz), 4.37 (1H, s), 3.56–3.63 (1H, m), 3.32 (1H, m), 2.57 (1H, s), 2.33–2.36 (2H, m), 2.28 (2H, m), 2.12–2.25 (3H, m), 1.77–1.88 (7H, m), 1.72 (3H, s), 1.50–1.59 (3H, m), 1.37 (3H, s), 1.25–1.30 (1H, m), 1.12 (3H, s), 0.70 (6H, d, J = 6.8 Hz) (Figure S88); ¹³C NMR (100 MHz, CDCl₃): δc 165.4 (C‐1′), 165.3 (C‐3′), 154.5 (C‐2″), 152.5 (C‐10″), 150.5 (C‐8″), 140.0 (C‐5), 137.7 (C‐4″), 135.7 (C‐6″), 122.5 (C‐5″), 121.4 (C‐3″), 118.2 (C‐6), 117.8 (C‐7″), 112.9 (C‐2′), 88.3 (C‐17), 88.0 (C‐14), 74.2 (C‐8), 72.2 (C‐12), 71.8 (C‐3), 58.5 (C‐13), 43.5 (C‐9), 42.1 (C‐4), 38.8 (C‐4′), 37.7 (C‐1), 36.8 (C‐10), 34.4 (C‐15), 34.0 (C‐7), 33.6 (C‐16), 30.9 (C‐2), 24.4 (C‐11), 20.7 (C‐5′), 20.4 (C‐6′), 18.4 (C‐19), 16.3 (C‐7′), 9.5 (C‐18) (Figure S89 and Table S3); (+)‐HR‐ESI‐MS m/z 655.2408 [M + H]⁺ (calcd for C₃₄H₄₄N₂O₆Br, 655.2383) (Figure S90).

4.1.3.8. 21‐(3,5‐Dibromoquinolin‐2‐yl)‐Caudatin (2h)

Obtained as a yellow solid (23.5 mg, 31.4%) from caudatin (1). ¹H NMR (400 MHz, CDCl₃): δ _H 8.09 (1H, d, J = 8.7 Hz), 7.89 (1H, d, J = 8.7 Hz), 7.81 (1H, s), 7.68 (1H, m), 5.40 (1H, s), 4.80–4.83 (1H, dd, J = 11.1, 3.8 Hz), 4.36 (1H, s), 3.52–3.60 (1H, m), 3.29 (1H, m), 2.63 (1H, s), 2.32–2.35 (2H, m), 2.27 (2H, m), 2.16–2.21 (3H, m), 1.73–1.89 (7H, m), 1.72 (3H, s), 1.49–1.61 (3H, m), 1.36 (3H, s), 1.25–1.31 (1H, m), 1.12 (3H, s), 0.71 (6H, d, J = 6.9 Hz) (Figure S91); ¹³C NMR (100 MHz, CDCl₃): δc 165.4 (C‐1′, C‐3′), 162.2 (C‐2″), 142.0 (C‐10″), 139.9 (C‐5), 135.8 (C‐8″), 135.4 (C‐4″), 129.1 (C‐5″), 128.9 (C‐6″), 120.9 (C‐9″), 119.8 (C‐6), 118.6 (C‐7″), 118.5 (C‐3″), 113.1 (C‐2′), 88.4 (C‐17), 88.1 (C‐14), 74.3 (C‐8), 72.4 (C‐12), 72.1 (C‐3), 58.2 (C‐13), 43.5 (C‐9), 42.2 (C‐4), 38.9 (C‐4′), 37.8 (C‐1), 36.9 (C‐10), 34.6 (C‐7, C‐15), 33.1 (C‐16), 31.0 (C‐2), 24.5 (C‐11), 20.8 (C‐5′), 20.5 (C‐6′), 18.5 (C‐19), 16.3 (C‐7′), 9.3 (C‐18) (Figure S92 and Table S3); (+)‐HR‐ESI‐MS m/z 732.1518 [M + H]⁺ (calcd for C₃₅H₄₄NO₆Br₂, 732.1535) (Figure S93).

4.1.4. Cell Lines and Culture Conditions

Four human cancer cell lines were applied in the cytotoxicity evaluation: MCF‐7 human breast adenocarcinoma cells (Research Resource Identifier, RRID: CVCL_0031), H1299 human non‐small cell lung carcinoma cells (RRID: CVCL_0060), HeLa human cervical carcinoma cells (RRID: CVCL_0030), HepG2 human hepatocellular carcinoma cells (RRID: CVCL_0027). All cell lines were purchased from the American Type Culture Collection (ATCC, Manassas, VA, USA). MCF‐7 and H1299 cells were maintained in RPMI‐1640 medium, while HeLa and HepG2 cells were cultured in Dulbecco's modified Eagle's medium (DMEM). All media were supplemented with 10% fetal bovine serum (FBS; ExCell Bio, Shanghai, China) and 1% penicillin‐streptomycin solution (Gibco, Grand Island, NY, USA). Cells were incubated at 37°C in a humidified atmosphere containing 5% CO₂ and 98% humidity.

4.1.5. Cytotoxicity Assay (MTT Assay)

All tested compounds (1, 1a–1w, and 2a–2h) and colchicine (positive control) were dissolved in dimethyl sulfoxide (DMSO) and diluted to the appropriate concentrations with culture medium. Cells in the logarithmic growth phase were seeded into 96‐well plates at a density of 5000 cells per well and incubated overnight to allow adhesion. The cells were treated with various concentrations of the tested compounds for 48 h. After incubation, 10 µL of MTT solution (5 mg/mL in phosphate‐buffered saline) was added to each well, and the plates were incubated for an additional 4 h. Then, 150 µL of DMSO was added to each well to dissolve the formazan crystals. The absorbance was measured at 570 nm with a microplate reader, and the half‐maximal inhibitory concentration (IC₅₀) values were calculated from the dose‐response curves. All experiments were performed in triplicate, and the results are expressed as the mean ± standard deviation (SD).

4.1.6. Cell Apoptosis Assay

HepG2 cells were seeded in 6‐well plates at a density of 1 × 10⁵ cells/well and incubated overnight to allow cell adhesion. Cells were then treated with 1b at the indicated concentrations (5, 10, and 30 µM) for 48 h. After treatment, both adherent and floating cells were harvested, washed with ice‐cooled annexin‐binding buffer, and stained with Annexin V‐FITC (1 µg/mL) and PI (5 µg/mL) for 10 min at room temperature in the dark. Flow cytometric detection and quantification were performed on a FACSCanto II flow cytometer (Becton Dickinson, NJ, USA). Early apoptotic cells were defined as Annexin V‐positive/PI‐negative, and late apoptotic cells were defined as Annexin V/PI double‐positive. The total apoptotic rate was calculated as the sum of the early and late apoptotic populations.

4.1.7. Cell Cycle Analysis

HepG2 cells were seeded into 6‐well culture plates at a density of 1 × 10⁵ cells per well and incubated overnight to allow complete cell adhesion. Subsequently, the cells were treated with 1b at the indicated concentrations (5, 10, and 30 µM) for 48 h. After treatment, the cells were harvested, washed twice with ice‐cooled phosphate‐buffered saline (PBS), and fixed with ice‐cooled 70% ethanol at 4°C overnight. The fixed cells were then washed with PBS and resuspended in PBS containing RNase A (10 mg/mL) and PI (50 mg/mL), followed by incubation for 30 min at room temperature in the dark. Finally, the cell cycle distribution of the stained samples was analyzed on a FACSCanto II flow cytometer.

Author Contributions

Xiao‐San Li and Xue‐Mei Yang designed the experiments. He‐Hui Zhan, Xin‐Hong Wang, Tong‐Xin Zheng, Bing‐Bing Li, Hui‐Ting Chen, An‐Yu Su, and Li Liu collected and curated the data. He‐Hui Zhan wrote the article. Xiao‐San Li, Xue‐Mei Yang, and Hui Luo supervised the study and and writing – review and editing. Xiao‐San Li and Hui Luo provided resources for this study. All the authors reviewed the article.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supporting File 1: cbdv71821‐sup‐0001‐SuppMat.doc

CBDV-23-e71821-s001.doc^{(36KB, doc)}

Supporting File 2: cbdv71821‐sup‐0002‐SuppMat.docx

CBDV-23-e71821-s002.docx^{(23.6MB, docx)}

Acknowledgments

This work was financially supported by grants from for the Economic Development of Marine Economy of Guangdong Province, China (GDNRC [2022]38), the “Clinical + Basic” Scientific Innovation Special Project of Guangdong Medical University (GDMUZDCG25020 and GDMUZDCG25023), and the Undergraduate Innovation and Entrepreneurship Education Base Project of Guangdong Medical University (JDXM2024094, JDXM2025049, JDXM2025086, JDXM2025124, and JDXM2025189).

Contributor Information

Xiao‐San Li, Email: lixiaosan2018@163.com.

Xue‐Mei Yang, Email: xuemeiyang131@163.com.

Hui Luo, Email: luohui@gdmu.edu.cn.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

References

1. Ma S., Jiang W., Li Q., et al., “Design, Synthesis, and Study of the Insecticidal Activity of Novel Steroidal 1,3,4‐Oxadiazoles,” Journal of Agricultural and Food Chemistry 69 (2021): 11572–11581, 10.1021/acs.jafc.1c00088. [DOI] [PubMed] [Google Scholar]
2. Singh R., Thota S., and Bansal R., “Studies on 16,17‐Pyrazoline Substituted Heterosteroids as Anti‐Alzheimer and Anti‐Parkinsonian Agents Using LPS Induced Neuroinflammation Models of Mice and Rats,” ACS Chemical Neuroscience 9 (2018): 272–283, 10.1021/acschemneuro.7b00303. [DOI] [PubMed] [Google Scholar]
3. Singh R. and Bansal R., “Investigations on 16‐Arylideno Steroids as a New Class of Neuroprotective Agents for the Treatment of Alzheimer's and Parkinson's Diseases,” ACS Chemical Neuroscience 8 (2017): 186–200, 10.1021/acschemneuro.6b00313. [DOI] [PubMed] [Google Scholar]
4. Shi Y. K., Wang B., Shi X. L., et al., “Synthesis and Biological Evaluation of New Steroidal Pyridines as Potential Anti‐Prostate Cancer Agents,” European Journal of Medicinal Chemistry 148 (2018): 438–451, 10.1016/j.ejmech.2017.12.094. [DOI] [PubMed] [Google Scholar]
5. Romero‐López A., Montiel‐Smith S., Meza‐Reyes S., Merino‐Montiel P., and Vega‐Baez J. L., “Synthesis of Steroidal Derivatives Containing Substituted, Fused and Spiro Pyrazolines,” Steroids 87 (2014): 86–92, 10.1016/j.steroids.2014.05.013. [DOI] [PubMed] [Google Scholar]
6. Iványi Z., Szabó N., Huber J., et al., “Synthesis of D‐Ring‐Substituted (5′R)‐ and (5′S)‐17β‐Pyrazolinylandrostene Epimers and Comparison of Their Potential Anticancer Activities,” Steroids 77 (2012): 566–574, 10.1016/j.steroids.2012.02.001. [DOI] [PubMed] [Google Scholar]
7. Li J., Huo H., Guo R., et al., “Facile and Efficient Access to Androsten‐17‐(1′,3′,4′)‐Pyrazoles and Androst‐17β‐(1′,3′,4′)‐Pyrazoles via Vilsmeier Reagents, and Their Antiproliferative Activity Evaluation In Vitro,” European Journal of Medicinal Chemistry 130 (2017): 1–14, 10.1016/j.ejmech.2017.02.033. [DOI] [PubMed] [Google Scholar]
8. Bilal Tufail M., Aamir Javed M., Ikram M., et al., “Synthesis, Pharmacological Evaluation and Molecular Modelling Studies of Pregnenolone Derivatives as Inhibitors of Human Dihydrofolate Reductase,” Steroids 168 (2021): 108801, 10.1016/j.steroids.2021.108801. [DOI] [PubMed] [Google Scholar]
9. Song J.‐R., Li N., Wei Y.‐L., Lu F.‐L., and Li D.‐P., “Design and Synthesis of Mogrol Derivatives Modified on A Ring With Anti‐Inflammatory and Anti‐Proliferative Activities,” Bioorganic & Medicinal Chemistry Letters 74 (2022): 128924, 10.1016/j.bmcl.2022.128924. [DOI] [PubMed] [Google Scholar]
10. Song J. R., Li N., and Li D. P., “Synthesis and Anti‐Proliferation Activity of Mogrol Derivatives Bearing Quinoline and Triazole Moieties,” Bioorganic & Medicinal Chemistry Letters 42 (2021): 128090, 10.1016/j.bmcl.2021.128090. [DOI] [PubMed] [Google Scholar]
11. Banday A. H., Iqbal Zargar M., and Ganaie B. A., “Synthesis and Antimicrobial Studies of Chalconyl Pregnenolones,” Steroids 76 (2011): 1358–1362, 10.1016/j.steroids.2011.07.001. [DOI] [PubMed] [Google Scholar]
12. Maurya S. W., Dev K., Singh K. B., et al., “Synthesis and Biological Evaluation of Heterocyclic Analogues of Pregnenolone as Novel Anti‐Osteoporotic Agents,” Bioorganic & Medicinal Chemistry Letters 27 (2017): 1390–1396, 10.1016/j.bmcl.2017.02.004. [DOI] [PubMed] [Google Scholar]
13. Scherbakov A. M., Zavarzin I. V., Vorontsova S. K., et al., “Synthesis and Evaluation of the Antiproliferative Activity of Benzylidenes of 16‐Dehydroprogesterone Series,” Steroids 138 (2018): 91–101, 10.1016/j.steroids.2018.06.013. [DOI] [PubMed] [Google Scholar]
14. Mazumder R., Ichudaule, Ghosh A., Deb S., and Ghosh R., “Significance of Chalcone Scaffolds in Medicinal Chemistry,” Topics in Current Chemistry 382 (2024): 22, 10.1007/s41061-024-00468-7. [DOI] [PubMed] [Google Scholar]
15. Smirnova I., Draghici G., Kazakova O., et al., “Hollongdione Arylidene Derivatives Induce Antiproliferative Activity Against Melanoma and Breast Cancer Through Pro‐Apoptotic and Antiangiogenic Mechanisms,” Bioorganic Chemistry 119 (2022): 105535, 10.1016/j.bioorg.2021.105535. [DOI] [PubMed] [Google Scholar]
16. Lone I. H., Khan K. Z., Fozdar B. I., and Hussain F., “Synthesis Antimicrobial and Antioxidant Studies of New Oximes of Steroidal Chalcones,” Steroids 78 (2013): 945–950, 10.1016/j.steroids.2013.05.015. [DOI] [PubMed] [Google Scholar]
17. Ruginsk B. E., Zattoni I. F., Gomes De Oliveira A. H., et al., “New Players From the Old Chalcone Scaffold: Synthesis, Identification, and Characterization of New Potent ABCG2 Inhibitors,” European Journal of Medicinal Chemistry 299 (2025): 118077, 10.1016/j.ejmech.2025.118077. [DOI] [PubMed] [Google Scholar]
18. Zhao L., Chen J., Xu M.‐F., et al., “Design, Synthesis and Structure‐Activity Relationship of 5′‐Prenylated Chalcone Derivatives Inhibited the Proliferation of Human Non‐Small Cell Lung Cancer Cells via Inducing Ferroptosis,” Bioorganic Chemistry 166 (2025): 109135, 10.1016/j.bioorg.2025.109135. [DOI] [PubMed] [Google Scholar]
19. Saifullah M. K., Ahasan, Kaleem M., et al., “A Comprehensive Review of Structure Activity Relationships: Exploration of Chalcone Derivatives as Anticancer Agents, Target‐Based and Cell Line‐Specific Insights,” Medicine in Drug Discovery 28 (2025): 100230, 10.1016/j.medidd.2025.100230. [DOI] [Google Scholar]
20. Abd El‐Lateef H. M., Alharbi T. H., Fayad E., et al., “Novel Quinolin‐4‐Ylcarbonylhydrazine Having N‐(3‐Arylacryloyl) Moiety: Design, Synthesis and Biological Evaluation as Potential Cytotoxic Agents Against MDA‐MB‐231 via Tubulin Assembly Inhibition,” Journal of Molecular Structure 1321 (2025): 140214, 10.1016/j.molstruc.2024.140214. [DOI] [Google Scholar]
21. Hammouda M. M., Elattar K. M., Rashed M. M., and Osman A. M. A., “Synthesis and Biological Activities of Bicyclic Pyridines Integrated Steroid Hybrid,” Steroids 199 (2023): 109287, 10.1016/j.steroids.2023.109287. [DOI] [PubMed] [Google Scholar]
22. Iqbal A. and Siddiqui T., “A Review on Synthesis and Biological Activities of D‐Ring Modified Pregnenolone,” Steroids 170 (2021): 108827, 10.1016/j.steroids.2021.108827. [DOI] [PubMed] [Google Scholar]
23. Rajendran S., Sivalingam K., Karnam Jayarampillai R. P., Wang W.‐L., and Salas C. O., “Friedländer's Synthesis of Quinolines as a Pivotal Step in the Development of Bioactive Heterocyclic Derivatives in the Current Era of Medicinal Chemistry,” Chemical Biology & Drug Design 100 (2022): 1042–1085, 10.1111/cbdd.14044. [DOI] [PubMed] [Google Scholar]
24. Bensalah D., Amri N., Mukhrish Y. E., Koko W. S., and Hamdi N., “Synthesis and Pharmacological Properties of Coumarin‐Chalcones,” MethodsX 11 (2023): 102488, 10.1016/j.mex.2023.102488. [DOI] [PMC free article] [PubMed] [Google Scholar]
25. Chen Y.‐F., Liu X.‐H., Li Z.‐Y., et al., “Chalcones and Their Derivatives as Inhibitors of Key ABC Transporters (ABCB1, ABCG2) to Overcome Tumor Multidrug Resistance,” Bioorganic Chemistry 166 (2025): 109105, 10.1016/j.bioorg.2025.109105. [DOI] [PubMed] [Google Scholar]
26. Djiemeny Ngueta A., Roy J., and Poirier D., “Chemical Synthesis, NMR Characterization, and Anticancer Activity of Androstene Derivatives With a C17‐Side Chain,” Steroids 186 (2022): 109064, 10.1016/j.steroids.2022.109064. [DOI] [PubMed] [Google Scholar]
27. Banday A. H., Mir B. P., Lone I. H., et al., “Studies on Novel D‐Ring Substituted Steroidal Pyrazolines as Potential Anticancer Agents,” Steroids 75 (2010): 805–809, 10.1016/j.steroids.2010.02.014. [DOI] [PubMed] [Google Scholar]
28. Perreault M., Maltais R., Roy J., et al., “Induction of Endoplasmic Reticulum Stress by Aminosteroid Derivative RM‐581 Leads to Tumor Regression in PANC‐1 Xenograft Model,” Investigational New Drugs 37 (2018): 431–440, 10.1007/s10637-018-0643-4. [DOI] [PubMed] [Google Scholar]
29. Hou Q., Lin X., Lu X., et al., “Discovery of Novel Steroidal‐Chalcone Hybrids With Potent and Selective Activity Against Triple‐Negative Breast Cancer,” Bioorganic & Medicinal Chemistry 28 (2020): 115763, 10.1016/j.bmc.2020.115763. [DOI] [PubMed] [Google Scholar]
30. Goswami M. J., Borah M., Hati Boruah J. L., et al., “Synthesis of Chalconoyl Pregnenolones as Antimicrobial, Antidiabetic and Antioxidant Agents,” Chemical Papers 78 (2024): 9037–9050, 10.1007/s11696-024-03725-7. [DOI] [Google Scholar]
31. Cai X., Sha F., Zhao C., et al., “Synthesis and Anti‐Inflammatory Activity of Novel Steroidal Chalcones With 3β‐Pregnenolone Ester Derivatives in RAW 264.7 Cells in Vitro,” Steroids 171 (2021): 108830, 10.1016/j.steroids.2021.108830. [DOI] [PubMed] [Google Scholar]
32. Wasfi A. A.‐M., Al‐Masoudi N. A., Saeed B. A., et al., “Synthesis, In Vitro Anti‐HIV Activity, Cytotoxicity, and Computational Studies of Some New Steroids and Their Pyrazoline and Oxime Analogues,” Russian Journal of Bioorganic Chemistry 46 (2020): 822–836, 10.1134/S1068162020050039. [DOI] [Google Scholar]
33. Gu X. J. and Hao D. C., “Recent Advances in Phytochemistry and Pharmacology of C₂₁ Steroid Constituents From Cynanchum Plants,” Chinese Journal of Natural Medicines 14 (2016): 321–334, 10.3724/SP.J.1009.2016.00321. [DOI] [PubMed] [Google Scholar]
34. Li X. S., Yang X. M., Ding W. J., et al., “New C₂₁‐Steroidal Aglycones From the Roots of Cynanchum otophyllum and Their Anticancer Activity,” Fitoterapia 149 (2021): 104833, 10.1016/j.fitote.2021.104833. [DOI] [PubMed] [Google Scholar]
35. Tan Z. W., Xie S., Hu S. Y., et al., “Caudatin Targets TNFAIP1/NF‐κB and Cytochrome C/Caspase Signaling to Suppress Tumor Progression in Human Uterine Cancer,” International Journal of Oncology 49 (2016): 1638–1650, 10.3892/ijo.2016.3662. [DOI] [PubMed] [Google Scholar]
36. Bailly C., “Anticancer Properties of Caudatin and Related C‐21 Steroidal Glycosides From Cynanchum Plants,” Steroids 172 (2021): 108855, 10.1016/j.steroids.2021.108855. [DOI] [PubMed] [Google Scholar]
37. Fei H. R., Chen H. L., Xiao T., et al., “Caudatin Induces Cell Cycle Arrest and Caspase‐Dependent Apoptosis in HepG2 Cell,” Molecular Biology Reports 39 (2012): 131–138, 10.1007/s11033-011-0721-6. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supporting File 1: cbdv71821‐sup‐0001‐SuppMat.doc

CBDV-23-e71821-s001.doc^{(36KB, doc)}

Supporting File 2: cbdv71821‐sup‐0002‐SuppMat.docx

CBDV-23-e71821-s002.docx^{(23.6MB, docx)}

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

[cbdv71821-bib-0001] 1. Ma S., Jiang W., Li Q., et al., “Design, Synthesis, and Study of the Insecticidal Activity of Novel Steroidal 1,3,4‐Oxadiazoles,” Journal of Agricultural and Food Chemistry 69 (2021): 11572–11581, 10.1021/acs.jafc.1c00088. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0002] 2. Singh R., Thota S., and Bansal R., “Studies on 16,17‐Pyrazoline Substituted Heterosteroids as Anti‐Alzheimer and Anti‐Parkinsonian Agents Using LPS Induced Neuroinflammation Models of Mice and Rats,” ACS Chemical Neuroscience 9 (2018): 272–283, 10.1021/acschemneuro.7b00303. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0003] 3. Singh R. and Bansal R., “Investigations on 16‐Arylideno Steroids as a New Class of Neuroprotective Agents for the Treatment of Alzheimer's and Parkinson's Diseases,” ACS Chemical Neuroscience 8 (2017): 186–200, 10.1021/acschemneuro.6b00313. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0004] 4. Shi Y. K., Wang B., Shi X. L., et al., “Synthesis and Biological Evaluation of New Steroidal Pyridines as Potential Anti‐Prostate Cancer Agents,” European Journal of Medicinal Chemistry 148 (2018): 438–451, 10.1016/j.ejmech.2017.12.094. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0005] 5. Romero‐López A., Montiel‐Smith S., Meza‐Reyes S., Merino‐Montiel P., and Vega‐Baez J. L., “Synthesis of Steroidal Derivatives Containing Substituted, Fused and Spiro Pyrazolines,” Steroids 87 (2014): 86–92, 10.1016/j.steroids.2014.05.013. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0006] 6. Iványi Z., Szabó N., Huber J., et al., “Synthesis of D‐Ring‐Substituted (5′R)‐ and (5′S)‐17β‐Pyrazolinylandrostene Epimers and Comparison of Their Potential Anticancer Activities,” Steroids 77 (2012): 566–574, 10.1016/j.steroids.2012.02.001. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0007] 7. Li J., Huo H., Guo R., et al., “Facile and Efficient Access to Androsten‐17‐(1′,3′,4′)‐Pyrazoles and Androst‐17β‐(1′,3′,4′)‐Pyrazoles via Vilsmeier Reagents, and Their Antiproliferative Activity Evaluation In Vitro,” European Journal of Medicinal Chemistry 130 (2017): 1–14, 10.1016/j.ejmech.2017.02.033. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0008] 8. Bilal Tufail M., Aamir Javed M., Ikram M., et al., “Synthesis, Pharmacological Evaluation and Molecular Modelling Studies of Pregnenolone Derivatives as Inhibitors of Human Dihydrofolate Reductase,” Steroids 168 (2021): 108801, 10.1016/j.steroids.2021.108801. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0009] 9. Song J.‐R., Li N., Wei Y.‐L., Lu F.‐L., and Li D.‐P., “Design and Synthesis of Mogrol Derivatives Modified on A Ring With Anti‐Inflammatory and Anti‐Proliferative Activities,” Bioorganic & Medicinal Chemistry Letters 74 (2022): 128924, 10.1016/j.bmcl.2022.128924. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0010] 10. Song J. R., Li N., and Li D. P., “Synthesis and Anti‐Proliferation Activity of Mogrol Derivatives Bearing Quinoline and Triazole Moieties,” Bioorganic & Medicinal Chemistry Letters 42 (2021): 128090, 10.1016/j.bmcl.2021.128090. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0011] 11. Banday A. H., Iqbal Zargar M., and Ganaie B. A., “Synthesis and Antimicrobial Studies of Chalconyl Pregnenolones,” Steroids 76 (2011): 1358–1362, 10.1016/j.steroids.2011.07.001. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0012] 12. Maurya S. W., Dev K., Singh K. B., et al., “Synthesis and Biological Evaluation of Heterocyclic Analogues of Pregnenolone as Novel Anti‐Osteoporotic Agents,” Bioorganic & Medicinal Chemistry Letters 27 (2017): 1390–1396, 10.1016/j.bmcl.2017.02.004. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0013] 13. Scherbakov A. M., Zavarzin I. V., Vorontsova S. K., et al., “Synthesis and Evaluation of the Antiproliferative Activity of Benzylidenes of 16‐Dehydroprogesterone Series,” Steroids 138 (2018): 91–101, 10.1016/j.steroids.2018.06.013. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0014] 14. Mazumder R., Ichudaule, Ghosh A., Deb S., and Ghosh R., “Significance of Chalcone Scaffolds in Medicinal Chemistry,” Topics in Current Chemistry 382 (2024): 22, 10.1007/s41061-024-00468-7. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0015] 15. Smirnova I., Draghici G., Kazakova O., et al., “Hollongdione Arylidene Derivatives Induce Antiproliferative Activity Against Melanoma and Breast Cancer Through Pro‐Apoptotic and Antiangiogenic Mechanisms,” Bioorganic Chemistry 119 (2022): 105535, 10.1016/j.bioorg.2021.105535. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0016] 16. Lone I. H., Khan K. Z., Fozdar B. I., and Hussain F., “Synthesis Antimicrobial and Antioxidant Studies of New Oximes of Steroidal Chalcones,” Steroids 78 (2013): 945–950, 10.1016/j.steroids.2013.05.015. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0017] 17. Ruginsk B. E., Zattoni I. F., Gomes De Oliveira A. H., et al., “New Players From the Old Chalcone Scaffold: Synthesis, Identification, and Characterization of New Potent ABCG2 Inhibitors,” European Journal of Medicinal Chemistry 299 (2025): 118077, 10.1016/j.ejmech.2025.118077. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0018] 18. Zhao L., Chen J., Xu M.‐F., et al., “Design, Synthesis and Structure‐Activity Relationship of 5′‐Prenylated Chalcone Derivatives Inhibited the Proliferation of Human Non‐Small Cell Lung Cancer Cells via Inducing Ferroptosis,” Bioorganic Chemistry 166 (2025): 109135, 10.1016/j.bioorg.2025.109135. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0019] 19. Saifullah M. K., Ahasan, Kaleem M., et al., “A Comprehensive Review of Structure Activity Relationships: Exploration of Chalcone Derivatives as Anticancer Agents, Target‐Based and Cell Line‐Specific Insights,” Medicine in Drug Discovery 28 (2025): 100230, 10.1016/j.medidd.2025.100230. [DOI] [Google Scholar]

[cbdv71821-bib-0020] 20. Abd El‐Lateef H. M., Alharbi T. H., Fayad E., et al., “Novel Quinolin‐4‐Ylcarbonylhydrazine Having N‐(3‐Arylacryloyl) Moiety: Design, Synthesis and Biological Evaluation as Potential Cytotoxic Agents Against MDA‐MB‐231 via Tubulin Assembly Inhibition,” Journal of Molecular Structure 1321 (2025): 140214, 10.1016/j.molstruc.2024.140214. [DOI] [Google Scholar]

[cbdv71821-bib-0021] 21. Hammouda M. M., Elattar K. M., Rashed M. M., and Osman A. M. A., “Synthesis and Biological Activities of Bicyclic Pyridines Integrated Steroid Hybrid,” Steroids 199 (2023): 109287, 10.1016/j.steroids.2023.109287. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0022] 22. Iqbal A. and Siddiqui T., “A Review on Synthesis and Biological Activities of D‐Ring Modified Pregnenolone,” Steroids 170 (2021): 108827, 10.1016/j.steroids.2021.108827. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0023] 23. Rajendran S., Sivalingam K., Karnam Jayarampillai R. P., Wang W.‐L., and Salas C. O., “Friedländer's Synthesis of Quinolines as a Pivotal Step in the Development of Bioactive Heterocyclic Derivatives in the Current Era of Medicinal Chemistry,” Chemical Biology & Drug Design 100 (2022): 1042–1085, 10.1111/cbdd.14044. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0024] 24. Bensalah D., Amri N., Mukhrish Y. E., Koko W. S., and Hamdi N., “Synthesis and Pharmacological Properties of Coumarin‐Chalcones,” MethodsX 11 (2023): 102488, 10.1016/j.mex.2023.102488. [DOI] [PMC free article] [PubMed] [Google Scholar]

[cbdv71821-bib-0025] 25. Chen Y.‐F., Liu X.‐H., Li Z.‐Y., et al., “Chalcones and Their Derivatives as Inhibitors of Key ABC Transporters (ABCB1, ABCG2) to Overcome Tumor Multidrug Resistance,” Bioorganic Chemistry 166 (2025): 109105, 10.1016/j.bioorg.2025.109105. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0026] 26. Djiemeny Ngueta A., Roy J., and Poirier D., “Chemical Synthesis, NMR Characterization, and Anticancer Activity of Androstene Derivatives With a C17‐Side Chain,” Steroids 186 (2022): 109064, 10.1016/j.steroids.2022.109064. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0027] 27. Banday A. H., Mir B. P., Lone I. H., et al., “Studies on Novel D‐Ring Substituted Steroidal Pyrazolines as Potential Anticancer Agents,” Steroids 75 (2010): 805–809, 10.1016/j.steroids.2010.02.014. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0028] 28. Perreault M., Maltais R., Roy J., et al., “Induction of Endoplasmic Reticulum Stress by Aminosteroid Derivative RM‐581 Leads to Tumor Regression in PANC‐1 Xenograft Model,” Investigational New Drugs 37 (2018): 431–440, 10.1007/s10637-018-0643-4. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0029] 29. Hou Q., Lin X., Lu X., et al., “Discovery of Novel Steroidal‐Chalcone Hybrids With Potent and Selective Activity Against Triple‐Negative Breast Cancer,” Bioorganic & Medicinal Chemistry 28 (2020): 115763, 10.1016/j.bmc.2020.115763. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0030] 30. Goswami M. J., Borah M., Hati Boruah J. L., et al., “Synthesis of Chalconoyl Pregnenolones as Antimicrobial, Antidiabetic and Antioxidant Agents,” Chemical Papers 78 (2024): 9037–9050, 10.1007/s11696-024-03725-7. [DOI] [Google Scholar]

[cbdv71821-bib-0031] 31. Cai X., Sha F., Zhao C., et al., “Synthesis and Anti‐Inflammatory Activity of Novel Steroidal Chalcones With 3β‐Pregnenolone Ester Derivatives in RAW 264.7 Cells in Vitro,” Steroids 171 (2021): 108830, 10.1016/j.steroids.2021.108830. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0032] 32. Wasfi A. A.‐M., Al‐Masoudi N. A., Saeed B. A., et al., “Synthesis, In Vitro Anti‐HIV Activity, Cytotoxicity, and Computational Studies of Some New Steroids and Their Pyrazoline and Oxime Analogues,” Russian Journal of Bioorganic Chemistry 46 (2020): 822–836, 10.1134/S1068162020050039. [DOI] [Google Scholar]

[cbdv71821-bib-0033] 33. Gu X. J. and Hao D. C., “Recent Advances in Phytochemistry and Pharmacology of C₂₁ Steroid Constituents From Cynanchum Plants,” Chinese Journal of Natural Medicines 14 (2016): 321–334, 10.3724/SP.J.1009.2016.00321. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0034] 34. Li X. S., Yang X. M., Ding W. J., et al., “New C₂₁‐Steroidal Aglycones From the Roots of Cynanchum otophyllum and Their Anticancer Activity,” Fitoterapia 149 (2021): 104833, 10.1016/j.fitote.2021.104833. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0035] 35. Tan Z. W., Xie S., Hu S. Y., et al., “Caudatin Targets TNFAIP1/NF‐κB and Cytochrome C/Caspase Signaling to Suppress Tumor Progression in Human Uterine Cancer,” International Journal of Oncology 49 (2016): 1638–1650, 10.3892/ijo.2016.3662. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0036] 36. Bailly C., “Anticancer Properties of Caudatin and Related C‐21 Steroidal Glycosides From Cynanchum Plants,” Steroids 172 (2021): 108855, 10.1016/j.steroids.2021.108855. [DOI] [PubMed] [Google Scholar]

[cbdv71821-bib-0037] 37. Fei H. R., Chen H. L., Xiao T., et al., “Caudatin Induces Cell Cycle Arrest and Caspase‐Dependent Apoptosis in HepG2 Cell,” Molecular Biology Reports 39 (2012): 131–138, 10.1007/s11033-011-0721-6. [DOI] [PubMed] [Google Scholar]

PERMALINK

Design and Synthesis of Novel Caudatin Derivatives Containing Arylacryloyl and Quinolyl Substituents With Anticancer Activity

Xiao‐San Li

He‐Hui Zhan

Xin‐Hong Wang

Tong‐Xin Zheng

Bing‐Bing Li

Hui‐Ting Chen

An‐Yu Su

Li Liu

Xue‐Mei Yang

Hui Luo

ABSTRACT

1. Introduction

FIGURE 1.

2. Results and Discussion

2.1. Chemistry

2.1.1. Synthesis of Caudatin Derivatives With Arylacryloyl Substituents (1a–1w)

SCHEME 1.

2.1.2. Synthesis of Caudatin Derivatives With Quinolyl Substituents (2a–2h)

SCHEME 2.

2.2. Biological Evaluation

2.2.1. Antiproliferative Activities and Structure–Activity Relationships

TABLE 1.

2.2.2. Analysis of Cell Apoptosis

FIGURE 2.

2.2.3. Cell Cycle Study by Flow Cytometry

FIGURE 3.

3. Conclusions

4. Experimental Section

4.1. Chemistry

4.1.1. General Information

4.1.2. General Procedure for Synthesis of Caudatin Derivatives With Arylacryloyl Substituents (1a–1w)

4.1.2.1. (21E)‐21‐(Furan‐2‐ylmethylene)‐Caudatin (1a)

4.1.2.2. (21E)‐21‐(Thiophen‐2‐ylmethylene)‐Caudatin (1b)

4.1.2.3. (21E)‐21‐Benzylidene‐Caudatin (1c)

4.1.2.4. (21E)‐21‐(Pyridin‐3‐ylmethylene)‐Caudatin (1d)

4.1.2.5. (21E)‐21‐(Pyridin‐4‐ylmethylene)‐Caudatin (1e)

4.1.2.6. (21E)‐21‐(p‐Methylbenzylidene)‐Caudatin (1f)

4.1.2.7. (21E)‐21‐(p‐Methoxybenzylidene)‐Caudatin (1g)

4.1.2.8. (21E)‐21‐(2,4‐Dimethoxybenzylidene)‐Caudatin (1h)

4.1.2.9. (21E)‐21‐(p‐Acetamidobenzylidene)‐Caudatin (1i)

4.1.2.10. (21E)‐21‐(p‐Formylbenzylidene)‐Caudatin (1j)

4.1.2.11. (21E)‐21‐(m‐Formylbenzylidene)‐Caudatin (1k)

4.1.2.12. (21E)‐21‐(p‐Cyanobenzylidene)‐Caudatin (1l)

4.1.2.13. (21E)‐21‐(p‐Nitrobenzylidene)‐Caudatin (1m)

4.1.2.14. (21E)‐21‐(p‐Trifluoromethylbenzylidene)‐Caudatin (1n)

4.1.2.15. (21E)‐21‐(p‐Fluorobenzylidene)‐Caudatin (1o)

4.1.2.16. (21E)‐21‐(m‐Fluorobenzylidene)‐CAUDATIN (1p)

4.1.2.17. (21E)‐21‐(o‐Fluorobenzylidene)‐Caudatin (1q)

4.1.2.18. (21E)‐21‐(3,4‐Difluorobenzylidene)‐Caudatin (1r)

4.1.2.19. (21E)‐21‐(2,4‐Difluorobenzylidene)‐Caudatin (1s)

4.1.2.20. (21E)‐21‐(3,5‐Difluorobenzylidene)‐Caudatin (1t)

4.1.2.21. (21E)‐21‐(3,4,5‐Trifluorobenzylidene)‐Caudatin (1u)

4.1.2.22. (21E)‐21‐(p‐Chlorobenzylidene)‐Caudatin (1v)

4.1.2.23. (21E)‐21‐(p‐Bromobenzylidene)‐Caudatin (1w)

4.1.3. General Procedure for the Synthesis of Caudatin Derivatives With Quinolyl Substituents (2a–2h)

4.1.3.1. 21‐(Quinolin‐2‐yl)‐Caudatin (2a)

4.1.3.2. 21‐(Pyrido[2,3‐b]pyrazin‐2‐yl)‐Caudatin (2b)

4.1.3.3. 21‐(5‐Fluoroquinolin‐2‐yl)‐Caudatin (2c)

4.1.3.4. 21‐(6‐Chloroquinolin‐2‐Yl)‐Caudatin (2d)

4.1.3.5. 21‐(4‐Chloroquinolin‐2‐yl)‐Caudatin (2e)

4.1.3.6. 21‐(5‐Bromoquinolin‐2‐yl)‐Caudatin (2f)

4.1.3.7. 21‐(5‐Bromopyrido[2,3‐b]pyrazin‐2‐yl)‐Caudatin (2g)

4.1.3.8. 21‐(3,5‐Dibromoquinolin‐2‐yl)‐Caudatin (2h)

4.1.4. Cell Lines and Culture Conditions

4.1.5. Cytotoxicity Assay (MTT Assay)

4.1.6. Cell Apoptosis Assay

4.1.7. Cell Cycle Analysis

Author Contributions

Conflicts of Interest

Supporting information

Acknowledgments

Contributor Information

Data Availability Statement

References

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS