Efficient Synthesis of Aurone Mannich Bases and Evaluation of their Antineoplastic Activity in PC-3 Prostate Cancer Cells

Antonina V Popova; Mykhaylo S Frasinyuk; Svitlana P Bondarenko; Wen Zhang; Yanqi Xie; Zachary M Martin; Xianfeng Cai; Michael V Fiandalo; James L Mohler; Chunming Liu; David S Watt; Vitaliy M Sviripa

doi:10.1007/s11696-018-0485-8

. Author manuscript; available in PMC: 2022 Oct 12.

Published in final edited form as: Chem Zvesti. 2018 Apr 28;72(10):2443–2456. doi: 10.1007/s11696-018-0485-8

Efficient Synthesis of Aurone Mannich Bases and Evaluation of their Antineoplastic Activity in PC-3 Prostate Cancer Cells

Antonina V Popova ^a, Mykhaylo S Frasinyuk ^a,^b,^c, Svitlana P Bondarenko ^d, Wen Zhang ^b,^e, Yanqi Xie ^b,^c, Zachary M Martin ^b,^c, Xianfeng Cai ^b,^e, Michael V Fiandalo ^f, James L Mohler ^f, Chunming Liu ^b,^e, David S Watt ^b,^c,^e, Vitaliy M Sviripa ^c,^g,^*

PMCID: PMC9555813 NIHMSID: NIHMS1801848 PMID: 36238867

Abstract

An efficient method for regioselective synthesis of C-7 Mannich bases of 6-hydroxyaurones was accomplished by the N,N-dialkylaminomethylation using aminals prepared from dimethylamine, dipropylamine, bis(2-methoxyethyl)amine, N-methylbutylamine, N-methylbenzylamine, morpholine, piperidine, and 1-methylpiperazine. Further transformation of 7-(N,N-dialkylamino)methyl group in these aurones led to formation of C-7 acetoxymethyl and methoxymethyl derivatives of 6-hydroxyaurones, some of which showed promising inhibition of PC-3 prostate cancer cell proliferation in the high nanomolar to low micromolar range that exceeded that of cisplatin.

Keywords: 6-hydroxyаurones, Mannich base, aminomеthylation, prostate cancer

Graphical Abstract

graphic file with name nihms-1801848-f0001.jpg

Introduction

2-Benzylidenebenzofuran-3(2Н)-ones, commonly known as aurones, represent a subclass of flavonoids with pharmacological potential.^1–3 Semisynthetic aurones display antitubercular,⁴ anticancer,⁵ antimalarial⁶ activity, and aurones with tertiary amines, including Mannich bases, were reported as inhibitors of AChE,⁷ PIM1,⁸ and p38 MAP kinase⁹. Structure-activity relationships among the flavonoids, isoflavonoids, and semisynthetic aurones do not necessarily parallel one another,¹⁰ but the high CDK1/Cyclin B inhibitory activity of flavonoid Mannich bases^{11, 12} prompted us to consider auronoid Mannich bases for evaluation as antineoplastic agents. In contrast to flavonoids and isoflavonoids, reports on the synthesis and evaluation of auronoid Mannich bases were scarce. We ascribed this deficiency to poor yields encountered in the application of “classical Mannich reactions” to 6-hydroxyaurones 2 using aqueous paraformaldehyde and secondary amines in ethanol.⁶ Alternative methods for the synthesis of semisynthetic aurones introduced aminomethyl groups on alkoxy- or hydroxy-substituted benzofuran-3(2Н)-one derivatives^{8, 13} 1 prior to condensation with aryl or heteroaryl aldehydes to secure the semisynthetic aurones 2 (Ar = aryl or heteroaryl). Aminomethylation of benzofuran-3(2Н)-one (1) generally proceed in poor yields because of competitive condensation at C-2 leading to 2,2-bis-(N,N-dialkylamino)methyl 6-hydroxybenzofuran-3(2Н)-one derivatives.^{14, 15}

As a consequence, we explored a procedure for the direct aminomethylation of semisynthetic 6-hydroxyaurones 2 as a means of acquiring compounds for biological evaluation.

Results and Discussion

The important criteria to consider in developing of a synthesis of N,N-dialkylaminomethyl derivatives of 6-hydroxyaurones included efficiency, simplicity, and regioselectivity. 6-Hydroxy-2-benzylidenbenzofuran-3(2H)-one 2 (Ar = C₆H₅) possessed two nucleophilic centers at C-5 and C-7, excluding possible centers in the benzylidene ring, for Mannich reactions. The efficient and selective aminomethylation of unsymmetrical phenols depended on the structure of the substrate, the dialkylamine, solvent, the catalyst, the pH, and in particular, the aminomethylating agent. These agents include iminium salts or hemiaminals,^{16, 17} imines,^18–20 and, aminals^{21, 22} that effect the aminomethylation of a range of phenolic substrates.

For these reasons, we investigated the aminomethylation of 6-hydroxyaurones using various reagents and under conditions that included the following: [1] 40% aqueous formaldehyde and a secondary amine in refluxing ethanol; [2] 40% aqueous formaldehyde and a secondary amine hydrochloride in refluxing ethanol; and [3] 40% aqueous formaldehyde and a secondary amine under basic catalysis by 4-dimethylaminopyridine (DMAP), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or Et₃N in refluxing ethanol. We obtained the best yields using DMAP as a catalyst and using paraformaldehyde in place of aqueous formaldehyde. For example, the aminomethylation of aurone 2c with 1-methylpiperazine gave 21% yield of the compound 10c using aqueous formaldehyde without base, 32% yield using aqueous formaldehyde with DMAP, and 46% yield using paraformaldehyde with DMAP. The formation of 5,7-bisaminomethyl derivatives was observed in all cases under these reaction conditions. Carrying out the aminomethylation using N-hydroxymethylamines and N,N-bisaminomethanes (aminals) proved to be the most promising pathway for the synthesis of Mannich bases of aurones. For example, aminomethylation of aurone 2c using 4,4’-methylenebis(1-methylpiperazine) increased the yield of 10c to 80% of the desired product and simplified the purification of 10c by minimizing the amount of the 5,7-bisaminomethyl derivatives.

Further studies revealed that the aminomethylation of most 6-hydroxyaurones with aminals in isopropanol or, in case of aurone 2d, in 1,4-dioxane gave the best yields. In these cases, we observed the regiospecific formation of 7-N,N-dialkylaminomethyl derivatives of these aurones. When using aminals prepared from dimethylamine, dipropylamine, bis(2-methoxyethyl)amine, N-methylbutylamine, N-methylbenzylamine, morpholine, piperidine, and 1-methylpiperazine, we did not observe formation of any 5,7-bisaminomethyl derivatives. The desired 7-(N,N-dialkylamino)methyl-6-hydroxyaurones were isolated in 51–86% yield (Scheme 1). Formation of 7-(N,N-dialkylamino)methyl derivatives was confirmed by ¹H NMR in which the coupling constant (J = 8.4–8.5 Hz) between H-4 and H-5 excluded the regioisomeric 5-(N,N-dialkylamino)methyl-6-hydroxyaurones.

Scheme 1. — Synthesis of Mannich bases of 6-hydroxyaurones **3–11**. Reagents and conditions: a) CH₂(NR⁵R⁶)₂, i-PrOH, 80°C, 4–8 h; b) CH₂(NC₄H₈X)₂, i-PrOH, 80°C, 4–6 h

Heating 7-N,N-dialkylaminomethyl-8-hydroxymethylaurones 3a-3d with acetic anhydride in presence of potassium acetate afforded the corresponding diacetates 12a-12d in excellent yield (Scheme 2). Hydrolysis of 12 in methanol using hydrochloric acid led directly to formation of 7-methoxymethyl derivatives 13a-13d.

Scheme 2. — Conversion of *N,N*-dimethylaminomethyl derivatives **3a-3d** to acetoxymethyl- and methoxymethyl derivatives. Reagents and conditions: a, Ac₂O, KOAc; b, HCl, MeOH.

A screening program using inhibition of the proliferation of PC-3 prostate cancer cells revealed that several 6-hydroxyaurones 2–13 with C-7 N,N-dialkylaminomethyl, acetoxymethyl or methoxymethyl substituents exhibited antiproliferative activity in the low micromolar range (Table 1). In general, 7-(N,N-dialkylamino)methyl-6-hydroxyaurones possessed weak activity at these concentrations but provided access to 7-acetoxymethylaurones that were the most potent. Thus, compounds 12c and 12d inhibited the growth of PC-3 cells at 1 μM concentration to the extent of 86.0±2.2% and 87.1±4.0, respectively. Additional testing of 12c at a concentration of 300 nM showed good retention of this inhibition of cell proliferation (75.4±15.6%).

Table 1.

IC₅₀ Values (μM) and percent inhibition of PC-3 cell proliferation by cisplatin (positive control) and selected aurones.

Aurone	R¹	R²	R³	R⁴	C-7	Inhibition at 10 μM (%)	IC₅₀ (μM)
2a	H	H	H	H	H	7.1±22.6
2e	H	OMe	OMe	OMe	H	52.9±31.7
3a	H	H	H	H	CH₂NMe₂	9.3±6.5
3e	H	OMe	OMe	OMe	CH₂NMe₂	22.4±8.3
5c	H	OMe	OMe	H	CH₂N(Me)CH₂Ph	25.9±12.9
5d	H	OCH₂O		H	CH₂N(Me)CH₂Ph	8.8±13.8
5e	H	OMe	OMe	OMe	CH₂N(Me)CH₂Ph	63.0±4.8	3.9±0.28
6d	H	OCH₂O		H	CH₂NiPr₂	84.51±0	8.8±0.1
8a	H	H	H	H	1-piperidinylmethyl	6.5±19.5
8d	H	OCH₂O		H	1-piperidinylmethyl	11.7±4.8
9e	H	OMe	OMe	OMe	4-morpholinomethyl	31.4±2.5
10b	H	H	OMe	H	4-(1-methylpiperazinyl)-methyl	40.6±5.6
10c	H	OMe	OMe	H	4-(1-methylpiperazinyl)-methyl	45.8±10.0
11c	H	OMe	OMe	H	4-(1-(2-hydroxyethyl)piperazinyl)-methyl	47.9±19.8
12c	H	OMe	OMe	H	acetoxymethyl	99.5±0.1	0.74±0.03
12d	H	OCH₂O		H	acetoxymethyl	87.9±2.3	3.7±0.42
cisplatin							> 10

Open in a new tab

Conclusions

Various aminals (i.e., bis(N,N-dialkylamino)methanes) derived from aliphatic and alicyclic amines afforded the regiospecific aminomethylation of 6-hydroxyaurones 2 (Scheme 1). The resulting Mannich bases in turn provided ready access to aurones 12 and 13 bearing either acetoxy or methoxy groups, respectively. Although the initial focus of this work required the identification of a viable synthetic route to the desired compounds, we were pleased to find that various aurones possessed in vitro activity in a PC-3 cell proliferation assay. Several analogs (i.e., 5e, 6d, 12c and 12d) possessed IC₅₀ values against prostate cancer PC-3 cells that were larger than the IC₅₀ of cisplatin (i.e., cis-diamminedichloridoplatinum(II)), a therapeutic antineoplastic agent in current use. In general, the aurones 3–11 possessing 3,4-dimethoxy or 3,4-methylenedioxy groups in the C-2 benzylidene subunit were more active in a PC-3 cell proliferation assay than those aurones with no alkoxy groups in the C-2 benzylidene subunit (i.e., 2e > 2a; and 3e >3a). In general, the diacetoxy-substituted aurones 12 were more active in a PC-3 cell proliferation than the corresponding Mannich bases 3–11 (i.e., 12c > 10–11c, > 5c; and 12d > 8d > 5d). Exceptions to these generalizations were, however, noted (e.g., 6d ~ 12d), and future, additional SAR work will further define these distinctions.

Other factors, such as solubility and in vitro stability, presumably played a role in the results of these cell proliferation assays. The Mannich bases of aurones 3–11 were, as expected, slightly soluble in water, and aurone 6d with a C-7 N,N-(diisopropylamino)methyl substituent and with promising inhibitor activity was soluble at pH 5–6 in phosphate, citrate and acetate buffers. The corresponding diacetoxy compound 12d also showed promising activity but was insoluble in water. The methoxymethyl derivatives 13 were also insoluble in water, but were soluble, as expected, in slightly basic aqueous solution. Future studies will focus on: defining the stability of the most promising diacetoxy-substituted aurones 12 to esterases (i.e., metabolism studies); determining if these aurones generate ortho-quinone methide intermediates; utilizing biotinylated intermediates to determine molecular target(s); evaluating toxicity issues; and performing xenograft studies to evaluate in vivo activity.

Experimental

Chemistry

Cisplatin was obtained from Sigma Aldrich (St. Louis, MO 63146 USA). ¹H and ¹³C NMR spectra were recorded on a Varian 500 spectrometer (at 500 MHz or at 125 MHz, respectively) or on a Varian 400 spectrometer (at 400 MHz or at 100 MHz, respectively) in deuteriochloroform (CDCl₃) or deuterated dimethylsulfoxide (DMSO-d₆). IR spectra were recorded on a Bruker Vertex 70 FT/IR spectrometer. Melting points were determined in open capillarity tubes with a Buchi B-535 apparatus and were uncorrected. Mass spectra were obtained with an Agilent 1100 spectrometer under chemical ionization conditions.

General procedure for the synthesis of 6-hydroxyaurones 2a-2f.

To a stirred solution of 0.75 g (5 mmol) 6-hydroxybenzofuranone (1) in ethanol (5 mL) and N,N-dimethylformamide (DMF) (5 mL) was added aldehyde (5 mmol) and 1.15 mL of 50% KOH. The mixture was stirred at room temperature for 4–6 h. The mixture was poured into 30 mL of hot water with vigorous stirring and neutralized with concentrated HCl at pH of 1–2. The precipitate was filtered, washed with water, dried and recrystallized from DMF-MeOH.

(2Z)-2-Benzylidene-6-hydroxy-1-benzofuran-3(2H)-one (2a).

Yellow solid (87% yield); mp: 259–260^oC; IR (KBr): ν_max 3072, 2960, 1674, 1644, 1580, 1455, 1376, 1285, 1109, 770 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 6.72 (1H, dd, ³J = 8.4 Hz, ⁴J = 1.7 Hz, H-5), 6.78 (1H, s, H-2a), 6.80 (1H, d, ⁴J=1.7 Hz, H-7), 7.38 –7.53 (3H, m, H-3′, 4′, 5′), 7.63 (1H, d, ³J = 8.4 Hz, H-4), 7.94 (2H, d, ³J = 8.5 Hz, H-2′, 6′), 11.30 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, DMSO-d₆): δ 98.71, 110.41, 112.79, 113.18, 126.08, 129.04, 129.72, 131.12, 132.14, 147.45, 166.70, 168.05, 181.55 ppm; MS (CI): m/z 238.9 (MH⁺, 100). Anal. calcd for C₁₅H₁₀O₃: C, 75.62; H, 4.23. Found: C, 75.41; H, 4.05.

(2Z)-6-Hydroxy-2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (2b).

Yellow solid (85% yield); mp: 268 – 270^oC; IR (KBr): ν_max 3081, 2899, 2598, 1675, 1566, 1455, 1285, 1256, 1108 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.81 (3H, s, OMe-4ʹ), 6.71 (1H, dd, ³J = 8.5 Hz, ⁴J = 2.0 Hz, H-5), 6.77 – 6.81 (2H, m, H-2a, H-7), 7.05 (2H, d, ³J = 8.4 Hz, H-3ʹ, 5ʹ), 7.61 (1H, d, ³J = 8.5 Hz, H-4), 7.91 (2H, d, ³J = 8.4 Hz, H-2ʹ, 6ʹ), 11.17 ppm (1H, s, OH-6); ¹³C NMR (100 MHz, DMSO-d₆): δ 55.28, 98.46, 110.62, 112.81, 112.96, 114.48, 124.50, 125.65, 132.82, 146.05, 160.30, 166.11, 167.47, 181.08 ppm; MS (CI): m/z 269.1 (MH⁺, 100). Anal. calcd for C₁₆H₁₂O₄: C, 71.64; H, 4.51. Found: C, 71.45; H 4.38.

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-1-benzofuran-3(2H)-one (2c).

Yellow solid (87% yield); mp: 224 – 226^oC; IR (KBr): ν_max 3122, 1679, 1582, 1509, 1259, 1235, 1125, 1092, 1015 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.82, 3.83 (each 3H, 2s, OMe-3ʹ,4ʹ), 6.68 (1H, dd, ³J = 8.5 Hz, ⁴J = 1.8 Hz, H-5), 6.73 (1H, s, H-2a), 6.75 (1H, d, ⁴J = 1.8 Hz, H-7), 7.07 (1H, d,³J = 8.5 Hz, H-5ʹ), 7.54–7.60 ppm (3H, m, H-4, 2ʹ, 6ʹ); ¹³C NMR (100 MHz, DMSO-d₆): δ 55.50, 55.55, 98.56, 111.07, 111.86, 112.83, 112.96, 114.13, 124.65, 124.98, 125.66, 146.11, 148.61, 150.25, 166.11, 167.45, 181.06 ppm; MS (CI): m/z 299.1 (MH⁺, 100). Anal. calcd for C₁₇H₁₄O₅: C, 68.45; H, 4.73. Found: C, 68.31; H 4.51.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-1-benzofuran-3(2H)-one (2d).

Yellow solid (91% yield); mp: 321 – 323^oC (decomp); IR (KBr): ν_max 3057, 2890, 1668, 1616, 1542, 1446, 1405, 1329, 1253, 1102, 1034 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 6.11 (2H, s, OCH₂O), 6.71 (1H, dd, ³J = 8.5 Hz, ⁴J = 1.8 Hz, H-5), 6.74 (1H, s, H-2a), 6.81 (1H, d, ⁴J = 1.8 Hz, H-7), 7.04 (1H, d, ³J = 8.1 Hz, H-7ʹ), 7.47 (1H, dd, ³J = 8.1 Hz, ⁴J = 1.7 Hz, H-6ʹ), 7.55 (1H, d, ⁴J = 1.7 Hz, H-4ʹ), 7.60 ppm (1H, d, ³J = 8.5 Hz, H-4); ¹³C NMR (100 MHz, DMSO-d₆): δ 98.58, 101.59, 108.80, 109.95, 110.64, 112.78, 112.93, 125.66, 126.12, 126.79, 146.15, 147.70, 148.50, 166.35, 167.52, 181.04 ppm; MS (CI): m/z 283.3 (MH⁺, 100). Anal. calcd for C₁₆H₁₀O₅: C, 68.09; H, 3.57. Found: C, 67.95; H, 3.68.

(2Z)-6-Hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (2e).

Yellow solid (81% yield); mp: 254 – 256^oC; IR (KBr): ν_max 3271, 1678, 1637, 1582, 1454, 1315, 1242, 1129, 1108, 998 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.72 (3H, s, OMe-4ʹ), 3.85 (6H, s, OMe-3ʹ, 5ʹ), 6.72 (1H, dd, ³J = 8.4 Hz, ²J = 2.0 Hz, H-5), 6.75 (1H, s, H-2a), 6.82 (1H, d, ⁴J = 2.0 Hz, H-7), 7.30 (2H, s, H-2ʹ, 6ʹ), 7.61 (1H, d, ³J = 8.4 Hz, H-4), 11.19 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, DMSO-d₆): δ 55.94, 60.12, 98.68, 108.73, 110.73, 112.74, 112.92, 125.73, 127.38, 139.03, 146.68, 152.83, 166.28, 167.61, 181.13 ppm; MS (CI): m/z 329.1 (MH⁺, 100). Anal. calcd for C₁₈H₁₆O₆: C, 65.85; H, 4.91. Found: C, 65.62; H; 5.04.

(2Z)-6-Hydroxy-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (2f).

Yellow solid (78% yield); mp: 249 – 251^oC; IR (KBr): ν_max 3169, 2941, 1680, 1582, 1492, 1266, 1136, 1103, 1090, 976 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.78, 3.87, 3.88 (each 3H, s, OMe-2ʹ, 3ʹ, 4ʹ), 6.71 (1H, dd, ³J = 8.3 Hz, ⁴J = 1.9 Hz, H-5), 6.77 (1H, d, ⁴J = 1.9 Hz, H-7), 6.90 (1H, s, H-2a), 6.98 (1H, d, ³J = 8.9 Hz, H-5ʹ), 7.61 (1H, d, ³J = 8.3 Hz, H-4), 7.93 (1H, d, ³J = 8.9 Hz, H-6ʹ), 11.15 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, DMSO-d₆): δ 55.96, 60.42, 61.61, 98.50, 104.01, 108.45, 112.86, 112.92, 118.25, 125.73, 126.25, 141.55, 146.79, 152.80, 154.95, 166.19, 167.48, 181.09 ppm; MS (CI): m/z 329.1 (MH⁺, 100). Anal. calcd for C₁₈H₁₆O₆: C, 65.85; H, 4.91. Found: C, 65.98; H, 5.12.

General procedure for the synthesis of Mannich bases 3–11.

To a suspension of 2 mmol of 2a-f in 10 mL of isopropyl alcohol or 1,4-dioxane (in case of compound 1d) was added 2.2 mmol of aminal, and the mixture was refluxed for 4–6 h. The mixture was diluted with 10 mL of hexanes and cooled. The residue was filtered and recrystallized from an isopropanol-hexanes mixture.

(2Z)-2-Benzylidene-7-[(dimethylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (3a).

Yellow solid (77% yield); mp: 248 – 250^oC; IR (KBr): ν_max 3051, 2394, 1682, 1598, 1507, 1444, 1333, 1272, 1123, 1049 cm⁻¹; ¹H NMR (500 MHz, CDCl₃): δ 2.51 (6H, s, NMe₂), 3.99 (2H, s, CH₂-7), 6.67 (1H, d, ³J = 8.4 Hz, H-5), 6.78 (1H, s, H-2a), 7.36 – 7.49 (3H, m, H-3ʹ, 4ʹ, 5ʹ), 7.61 (1H, d, ³J = 8.4 Hz, H-4), 7.82 (2H, d, ³J = 8.8 Hz, H-2ʹ, 6ʹ), 10.69 ppm (1H, br. s, OH-7); ¹³C NMR (125 MHz, CDCl₃): δ 44.55, 54.64, 104.19, 111.37, 113.16, 113.84, 125.53, 129.00, 129.55, 131.21, 132.72, 148.08, 165.86, 168.12, 182.78 ppm; MS (CI): m/z 296.2 (MH⁺, 100). Anal. calcd for C₁₈H₁₇NO₃: C, 73.20; H, 5.80; N, 4.74. Found: C, 73.04; H, 5.54; N, 4.61.

(2Z)-7-[(Dimethylamino)methyl]-6-hydroxy-2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (3b).

Yellow solid (83% yield); mp: 171–173^oC; IR (KBr): ν_max 2960, 2836, 1692, 1600, 1509, 1252, 1126, 1036, 821 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.49 (6H, s, NMe₂), 3.85 (3H, s, OMe-4ʹ), 3.96 (2H, s, CH₂-7), 6.64 (1H, d, ³J = 8.5 Hz, H-5), 6.74 (1H, s, H-2a), 6.97 (2H, d, ³J = 8.9 Hz, H-3′, 5′), 7.58 (1H, d, ³J = 8.5 Hz, H-4), 7.77 (2H, d, ³J = 8.9 Hz, H-2′, 6′), 7.95 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, CDCl₃): δ 44.55, 54.72, 55.46, 104.21, 111.68, 113.43, 113.62, 114.56, 125.27, 125.35, 133.00, 146.97, 160.76, 165.48, 167.74, 182.73 ppm; MS (CI): m/z 326.2 (MH⁺, 100). Anal. calcd for C₁₉H₁₉NO₄: C, 70.14; H, 5.89; N, 4.30. Found: C, 69.90; H, 5.62; N, 4.55.

(2Z)-2-(3,4-Dimethoxybenzylidene)-7-[(dimethylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (3c).

Yellow solid (78% yield); mp: 91 – 93^oC; IR (KBr): ν_max 3451, 3387, 2834, 1672, 1588, 1514, 1455, 1336, 1266, 1122 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.45 (6H, s, NMe₂), 3.91 (2H, s, CH₂-7), 3.95, 3.98 (each 3H, 2s, OMe-3ʹ,4ʹ), 6.65 (1H, d, ³J = 8.3 Hz, H-5), 6.77 (1H, s, H-2a), 6.96 (1H, d,³J = 8.4 Hz, H-5ʹ), 7.42 (1H, dd, ³J = 8.3 Hz, ⁴J = 1.9 Hz, H-6ʹ), 7.50 (1H, d, ⁴J = 1.9 Hz, H-2ʹ), 7.61 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 44.74, 54.78, 55.85, 56.08, 104.22, 111.40, 111.95, 113.54, 113.63, 125.39, 125.43, 125.63, 147.10, 149.04, 150.54, 165.39, 167.46, 182.63 ppm; MS (CI): m/z 356.2 (MH⁺, 100). Anal. calcd for C₂₀H₂₁NO₅: C, 67.59; H, 5.96; N, 3.94. Found: C, 67.83; H, 6.17; N, 4.07.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-7-[(dimethylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (3d).

Yellow solid (84% yield); mp: 158 – 160^oC; IR (KBr): ν_max 2963, 2899, 1689, 1601, 1444, 1331, 1242, 1038 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.47 (6H, s, NMe₂), 3.94 (2H, s, CH₂-7), 6.05 (2H, s, OCH₂O), 6.64 (1H, d, ³J = 8.5 Hz, H-5), 6.72 (1H, s, H-2a), 6.89 (1H, d, ³J = 8.1 Hz, H-7ʹ), 7.24 – 7.27 (1H, m, H-6ʹ), 7.47 (1H, d, ⁴J = 1.6 Hz, H-4ʹ), 7.60 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 44.62, 54.98, 101.61, 104.50, 108.91, 110.31, 111.61, 113.37, 113.68, 125.17, 126.96, 127.12, 147.02, 148.20, 148.91, 165.37, 167.82, 182.64 ppm; MS (CI): m/z 340.0 (MH⁺, 100). Anal. calcd for C₁₉H₁₇NO₅: C, 67.25; H, 5.05; N, 4.13. Found: C, 66.98; H, 5.31; N, 4.42.

(2Z)-7-[(Dimethylamino)methyl]-6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (3e).

Yellow solid (76% yield); mp: 191 – 193^oC; IR (KBr): ν_max 3433, 2955, 1670, 1614, 1510, 1450, 1344, 1273, 1130, 1051 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.43 (6H, s, NMe₂), 3.88 (2H, s, CH₂-7 ), 3.92 (3H, s, OMе−4ʹ), 3.95 (6H, s, OMе−3ʹ, 5ʹ), 6.66 (1H, d, ³J = 8.5 Hz, H-5), 6.73 (1H, s, H-2a), 7.14 (2H, s, H-2ʹ, 6ʹ), 7.62 ppm (1H, d, ³J = 8.5 Hz, H-4); ¹³C NMR (100 MHz, DMSO-d₆): δ 43.62, 52.26, 55.82, 60.14, 103.65, 108.15, 108.89, 109.11, 115.07, 124.78, 127.90, 138.43, 147.63, 152.80, 166.27, 171.55, 179.71 ppm; MS (CI): m/z 386.2 (MH⁺, 100). Anal. calcd for C₂₁H₂₃NO₆: C, 65.44; H, 6.02; N, 3.63. Found: C, 65.21; H, 6.15; N, 3.49.

(2Z)-7-[(Dimethylamino)methyl]-6-hydroxy-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (3f).

Yellow solid (87% yield); mp: 152–154^oC; IR (KBr): ν_max 2940, 1678, 1599, 1496, 1453, 1278, 1122, 1090 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.47 (6H, s, NMe₂), 3.90, 3.95, 3.97 (each 3H, 3s, OMe-2ʹ, 3ʹ, 4ʹ), 3.93 (2H, s, CH₂-7), 6.65 (1H, d, ³J = 8.4 Hz, H-5), 6.84 (1H, d, ³J = 8.9 Hz, H-5ʹ), 7.21 (1H, s, H-2a), 7.62 (1H, d, ³J = 8.5 Hz, H-4), 7.94 (1H, d, ³J = 8.9 Hz, H-6ʹ), 8.24 ppm (1H, br. s, OH-7); ¹³C NMR (100 MHz, CDCl₃): δ 44.37, 54.32, 56.07, 60.90, 61.84, 103.80, 105.74, 107.73, 113.47, 119.63, 125.36, 126.53, 142.21, 147.57, 153.86, 155.13, 165.38, 167.43, 182.51 ppm; MS (CI): m/z 386.2 (MH⁺, 100). Anal. calcd for C₂₁H₂₃NO₆: C, 65.44; H, 6.02; N, 3.63. Found: C, 65.17; H, 5.83; N, 3.90.

(2Z)-7-{[Butyl(methyl)amino]methyl}−6-hydroxy-2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (4b).

Yellow solid (76% yield); mp: 112 – 114^oC; IR (KBr): ν_max 3421, 2958, 1664, 1606, 1510, 1460, 1257, 1130 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 0.88 (3H, t, ³J = 7.3 Hz, CH₂CH₂CH₂CH₃), 1.24– 1.38 (2H, m, CH₂CH₂CH₂CH₃), 1.52 – 1.69 (2H, m, CH₂CH₂CH₂CH₃), 2.43 (3H, s, NMe), 2.63– 2.78 (2H, m, CH₂CH₂CH₂CH₃), 3.82 (3H, s, OMe-4ʹ), 4.04 (2H, s, CH₂-7), 6.48 (1H, d, ³J = 8.6 Hz, H-5), 6.68 (1H, s, H-2a), 7.05 (2H, d, ³J = 8.8 Hz, H-3′, 5′), 7.45 (1H, d, ³J = 8.6 Hz, H-4), 7.90 ppm (2H, d, ³J = 8.8 Hz, H-2′, 6′); ¹³C NMR (100 MHz, DMSO-d₆): δ 13.71, 19.75, 27.87, 40.68, 51.17, 55.24, 55.73, 104.07, 109.03, 109.52, 114.41, 114.67, 124.33, 124.93, 132.53, 146.83, 159.91, 165.85, 171.15, 179.93 ppm; MS (CI): m/z 368.1 (MH⁺, 100). Anal. calcd for C₂₂H₂₅NO₄: C, 71.91; H, 6.86; N, 3.81. Found: C, 72.09; H, 6.63; N, 3.65.

(2Z)-7-{[Butyl(methyl)amino]methyl}−2-(3,4-dimethoxybenzylidene)-6-hydroxy-1-benzofuran-3(2H)-one (4c).

Yellow solid (73% yield); mp: 101 – 102^oC; IR (KBr): ν_max 2959, 1676, 1605, 1512, 1458, 1260, 1118 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 0.92 (3H, t, ³J = 7.4 Hz, CH₂CH₂CH₂CH₃), 1.27– 1.46 (2H, m, CH₂CH₂CH₂CH₃), 1.48 – 1.70 (2H, m, CH₂CH₂CH₂CH₃), 2.41 (3H, s, NMe), 2.53– 2.65 (2H, m, CH₂CH₂CH₂CH₃), 3.92, 3.95 (each 3H, 2s, OMe-3ʹ,4ʹ), 3.98 (2H, s, CH₂-7), 6.65 (1H, d, ³J = 8.5 Hz, H-5), 6.73 (1H, s, H-2a), 6.93 (1H, d,³J = 8.5 Hz, H-5ʹ), 7.38 (1H, dd, ³J = 8.5 Hz, ⁴J = 2.0 Hz, H-6ʹ), 7.45 (1H, d, ⁴J = 2.0 Hz, H-2ʹ), 7.58 ppm (1H, d, ³J = 8.5 Hz, H-4); ¹³C NMR (100 MHz, CDCl₃): δ 13.95, 20.41, 28.72, 41.37, 53.31, 55.83, 56.07, 57.09, 104.08, 111.39, 111.86, 113.47, 113.61, 113.67, 125.35, 125.40, 125.64, 147.12, 149.05, 150.52, 165.50, 167.62, 182.56 ppm; MS (CI): m/z 398.2 (MH⁺, 100). Anal. calcd for C₂₃H₂₇NO₅: C, 69.50; H, 6.85; N, 3.52. Found: C, 69.77; H, 7.03; N, 3.64.

(2Z)-7-{[Butyl(methyl)amino]methyl}−6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (4e).

Yellow solid (82% yield); mp: 147 – 149^oC; IR (KBr): ν_max 2959, 1677, 1603, 1511, 1459, 1334, 1274, 1117 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 0.93 (3H, t, ³J = 7.4 Hz, CH₂CH₂CH₂CH₃), 1.31– 1.43 (2H, m, CH₂CH₂CH₂CH₃), 1.56 – 1.68 (2H, m, CH₂CH₂CH₂CH₃), 2.43 (3H, s, NMe), 2.55– 2.77 (2H, m, CH₂CH₂CH₂CH₃), 3.91 (3H, s, OMе−4ʹ), 3.93 (6H, s, OMе−3ʹ, 5ʹ), 3.99 (2H, s, CH₂-7), 6.58 – 6.78 (2H, m, H-2a, 5), 7.12 (2H, s, H-2ʹ, 6ʹ), 7.60 (1H, d, ³J = 8.5 Hz, H-4), 10.29 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, CDCl₃): δ 13.95, 20.40, 28.50, 41.34, 53.12, 56.18, 57.10, 61.13, 103.95, 108.64, 111.67, 113.34, 113.84, 125.61, 128.08, 139.75, 147.67, 153.37, 165.69, 167.71, 182.50 ppm; MS (CI): m/z 428.2 (MH⁺, 100). Anal. calcd for C₂₄H₂₉NO₆: C, 67.43; H, 6.84; N, 3.28. Found: C, 67.18; H, 7.07; N, 3.08.

(2Z)-7-{[Benzyl(methyl)amino]methyl}−2-(3,4-dimethoxybenzylidene)-6-hydroxy-1-benzofuran-3(2H)-one (5c).

Yellow solid (71% yield); mp: 141 – 143^oC; IR (KBr): ν_max 2946, 2835, 1698, 1601, 1515, 1420, 1261, 1142, 1117, 1024 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.38 (3H, s, NMe), 3.73 (2H, s, NCH₂Ph), 3.92, 3.96 (each 3H, 2s, OMe-3ʹ, 4ʹ), 3.98 (2H, s, CH₂-7), 6.68 (1H, d, ³J = 8.5 Hz, H-5), 6.77 (1H, s, H-2a), 6.95 (1H, d,³J = 8.4 Hz, H-5ʹ), 7.28 – 7.43 (6H, m, H-6ʹ, NCH₂Ph), 7.49 (1H, d, ⁴J = 1.9 Hz, H-2ʹ), 7.62 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (100 MHz, DMSO-d₆): δ 40.87, 50.48, 55.30, 55.54, 60.46, 106.10, 110.50, 111.60, 111.78, 113.41, 124.32, 124.88, 125.13, 127.29, 128.23, 129.06, 137.02, 146.41, 148.56, 150.07, 165.58, 167.56, 180.79 ppm; MS (CI): m/z 432.2 (MH⁺, 100). Anal. calcd for C₂₆H₂₅NO₅: C, 72.37; H, 5.84; N, 3.25. Found: C, 72.16; H, 5.95; N, 3.42.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-7-{[benzyl(methyl)amino]methyl}−6-hydroxy-1-benzofuran-3(2H)-one (5d).

Yellow solid (69% yield; mp: 159 – 161^oC; IR (KBr): ν_max 2851, 1697, 1602, 1499, 1243, 1188, 1035 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.40 (3H, s, NMe), 3.77 (2H, s, NCH₂Ph), 4.03 (2H, s, CH₂-7), 6.07 (2H, s, OCH₂O), 6.68 (1H, d, ³J = 8.4 Hz, H-5), 6.74 (1H, s, H-2a), 6.90 (1H, d, ³J = 8.1 Hz, H-7ʹ), 7.22 – 7.43 (6H, m, H-6ʹ, NCH₂Ph), 7.48 (1H, d, ⁴J = 1.7 Hz, H-4ʹ), 7.62 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (100 MHz, CDCl₃): δ 41.38, 52.52, 61.31, 100.09, 101.64, 104.46, 108.94, 110.34, 111.76, 113.66, 125.35, 126.90, 127.16, 128.31, 128.93, 129.67, 135.39, 146.95, 148.23, 148.97, 165.49, 167.31, 182.62 ppm; MS (CI): m/z 416.2 (MH⁺, 100). Anal. calcd for C₂₅H₂₁NO₅: C, 72.28; H, 5.10; N, 3.37. Found: C, 72.43; H, 5.36; N, 3.09.

(2Z)-7-{[Benzyl(methyl)amino]methyl}−6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (5e).

Yellow solid (68% yield); mp: 144 – 146^oC; IR (KBr): ν_max 2938, 2837, 1685, 1599, 1452, 1262, 1132 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.39 (3H, s, NMe), 3.73 (2H, s, NCH₂Ph), 3.91 (6H, s, OMе−3ʹ, 5ʹ), 3.94 (3H, s, OMе−4ʹ), 3.97 (2H, s, CH₂-7), 6.70 (1H, d, ³J = 8.4 Hz, H-5), 6.74 (1H, s, H-2a), 7.14 (2H, s, H-2ʹ, 6ʹ), 7.29 – 7.41 (5H, m, NCH₂Ph), 7.64 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (100 MHz, CDCl₃): 41.63, 52.22, 56.12, 61.13, 61.36, 104.45, 108.60, 111.75, 113.61, 113.70, 125.52, 128.06, 128.41, 128.95, 129.76, 134.88, 139.71, 147.62, 153.34, 165.50, 167.24, 182.59 ppm; MS (CI): m/z 462.0 (MH⁺, 100). Anal. calcd for C₂₇H₂₇NO₆: C, 70.27; H, 5.90; N, 3.03. Found: C, 70.50; H, 6.18; N, 3.31.

(2Z)-7-{[Benzyl(methyl)amino]methyl}−6-hydroxy-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (5f).

Yellow solid (76% yield); mp: 139 – 141^oC; IR (KBr): ν_max 2940, 1692, 1601, 1460, 1256, 1133, 1091 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.40 (3H, s, NMe), 3.78 (2H, s, NCH₂Ph), 3.89, 3.95, 3.96 (each 3H, 3s, OMe-2ʹ, 3ʹ, 4ʹ), 4.04 (2H, s, CH₂-7), 6.71 (1H, d, ³J = 8.5 Hz, H-5), 6.82 (1H, d, ³J = 8.9 Hz, H-5ʹ), 7.21 (1H, s, H-2a), 7.29 – 7.44 (5H, m, NCH₂Ph), 7.63 (1H, d, ³J = 8.5 Hz, H-4), 7.92 ppm (1H, d, ³J = 8.9 Hz, H-6ʹ); ¹³C NMR (100 MHz, CDCl₃): δ 41.40, 52.43, 56.23, 61.04, 61.30, 61.98, 104.34, 105.93, 107.87, 113.51, 113.97, 119.82, 125.46, 126.71, 128.33, 128.95, 129.72, 135.33, 142.40, 147.70, 154.05, 155.29, 165.47, 167.01, 182.69 ppm; MS (CI): m/z 462.0 (MH⁺, 100). Anal. calcd for C₂₇H₂₇NO₆: C, 70.27; H, 5.90; N, 3.03. Found: C, 70.02; H, 5.65; N, 2.84.

(2Z)-2-(3,4-Dimethoxybenzylidene)-7-[(dipropylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (6c).

Yellow solid (73% yield); mp: 135 – 137^oC; IR (KBr): ν_max 2966, 1666, 1597, 1514, 1458, 1263, 1114, 1019 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 0.91 (6H, t, ³J = 7.4 Hz, N(CH₂CH₂CH₃)₂), 1.53 –1.72 (4H, m, N(CH₂CH₂CH₃)₂), 2.50 – 2.67 (4H, m, N(CH₂CH₂CH₃)₂), 3.91, 3.94 (each 3H, 2s, OMe-3ʹ,4ʹ), 4.01 (2H, s, CH₂-7), 6.61 (1H, d, ³J = 8.5 Hz, H-5), 6.71 (1H, s, H-2a), 6.91 (1H, d,³J = 8.2 Hz, H-5ʹ), 7.36 (1H, dd, ³J = 8.2 Hz, ⁴J = 2.0 Hz, H-6ʹ), 7.45 (1H, d, ⁴J = 2.0 Hz, H-2ʹ), 7.56 (1H, d, ³J = 8.5 Hz, H-4), 8.30 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, CDCl₃): δ 11.77, 19.27, 50.41, 55.71, 55.73, 56.02, 104.33, 111.32, 111.70, 113.26, 113.49, 113.71, 125.12, 125.37, 125.65, 147.14, 148.98, 150.44, 165.45, 167.94, 182.51 ppm; MS (CI): m/z 412.2 (MH⁺, 100). Anal. calcd for C₂₄H₂₉NO₅: C, 70.05; H, 7.10; N, 3.40. Found: C, 69.86; H, 7.35; N, 3.12.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-7-[(dipropylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (6d).

Yellow solid (72% yield); mp: 117 – 119^oC; IR (KBr): ν_max 2963, 2875, 1690, 1596, 1486, 1442, 1254, 1188, 1110, 1040 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 0.94 (6H, t, ³J = 7.4 Hz, N(CH₂CH₂CH₃)₂), 1.59 –1.76 (4H, m, N(CH₂CH₂CH₃)₂), 2.59 – 2.70 (4H, m, N(CH₂CH₂CH₃)₂), 4.05 (2H, s, CH₂-7), 6.04 (2H, s, OCH₂O), 6.64 (1H, d, ³J = 8.5 Hz, H-5), 6.71 (1H, s, H-2a), 6.88 (1H, d, ³J = 8.1 Hz, H-7ʹ), 7.21 – 7.27 (1H, m, H-6ʹ), 7.45 (1H, d, ⁴J = 1.7 Hz, H-4ʹ), 7.59 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 11.86, 19.67, 50.76, 56.01, 101.63, 104.66, 108.97, 110.35, 111.47, 113.21, 113.90, 125.09, 127.11, 127.12, 147.18, 148.24, 148.89, 165.56, 168.34, 182.67 ppm; MS (CI): m/z 396.0 (MH⁺, 100). Anal. calcd for C₂₃H₂₅NO₅: C, 69.86; H, 6.37; N, 3.54. Found: C, 69.60; H, 6.20; N, 3.48.

(2Z)-7-[(Dipropylamino)methyl]-6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (6e).

Yellow solid (65% yield); mp: 172 – 174^oC; IR (KBr): ν_max 3472, 2962, 1686, 1603, 1460, 1269, 1134, 1009 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 0.94 (6H, t, ³J = 7.4 Hz, N(CH₂CH₂CH₃)₂), 1.57 –1.65 (4H, m, N(CH₂CH₂CH₃)₂), 2.57– 2.60 (4H, m, N(CH₂CH₂CH₃)₂), 3.91 (3H, s, OMe-4ʹ), 3.94 (6H, s, OMe-3ʹ, 5ʹ), 4.00 (2H, s, CH₂-7), 6.63 (1H, d, ³J = 8.5 Hz, H-5), 6.72 (1H, s, H-2a), 7.14 (2H, s, H-2ʹ,6ʹ), 7.61 ppm (1H, d, ³J = 8.5 Hz, H-4); ¹³C NMR (100 MHz, DMSO-d₆): δ 11.41, 18.21, 49.35, 54.41, 55.72, 60.11, 103.92, 108.31, 109.78, 110.21, 114.28, 124.45, 127.67, 138.61, 147.28, 152.76, 165.26, 170.30, 180.21 ppm; MS (CI): m/z 442.3 (MH⁺, 100). Anal. calcd for C₂₅H₃₁NO₆: C, 68.01; H, 7.08; N, 3.17. Found: C, 68.15; H, 6.79; N, 2.99.

(2Z)-2-Benzylidene-7-{[bis(2-methoxyethyl)amino]methyl}−6-hydroxy-1-benzofuran-3(2H)-one (7a).

Yellow solid (69% yield); mp: 81 – 82^oC; IR (KBr): ν_max 2879, 1697, 1604, 128, 1187, 1128, 1105, 1039 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.96 (4H, t, ³J = 5.3 Hz, N(CH₂CH₂OMe)₂), 3.35 (6H, s, CH₂OCH₃), 3.59 (4H, t, ³J = 5.3 Hz, N(CH₂CH₂OMe)₂), 4.19 (2H, s, CH₂-7), 6.68 (1H, d, ³J = 8.4 Hz, H-5), 6.79 (1H, s, H-2a), 7.33 – 7.51 (3H, m, H-3ʹ, 4ʹ, 5ʹ), 7.61 (1H, d, ³J = 8.4 Hz, H-4), 7.85 ppm (2H, d, ³J = 8.8 Hz, H-2ʹ, 6ʹ); ¹³C NMR (125 MHz, CDCl₃): δ 50.15, 53.62, 58.93, 69.87, 105.39, 111.28, 113.35, 113.92, 125.25, 128.95, 129.51, 131.22, 132.76, 148.12, 165.94, 167.58, 182.94 ppm; MS (CI): m/z 384.0 (MH⁺, 100). Anal. calcd for C₂₂H₂₅NO₅: C, 68.91; H, 6.57; N, 3.65. Found: C, 69.15; H, 6.39; N, 3.71.

(2Z)-7-{[Bis(2-methoxyethyl)amino]methyl}−6-hydroxy-2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (7b).

Yellow solid (83% yield); mp: 109 – 111^oC; IR (KBr): ν_max 3421, 2935, 1687, 1601, 1512, 1400, 1255, 1132, 1038 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 2.84 (4H, t, ³J = 5.3 Hz, N(CH₂CH₂OMe)₂), 3.22 (6H, s, CH₂OCH₃), 3.51 (4H, t, ³J = 5.5 Hz, N(CH₂CH₂OMe)₂), 3.82 (3H, s, OMe-4ʹ), 4.10 (2H, s, CH₂-7), 6.63 (1H, d, ³J = 8.4 Hz, H-5), 6.76 (1H, s, H-2a), 7.05 (2H, d, ³J = 8.8 Hz, H-3′, 5′), 7.52 (1H, d, ³J = 8.4 Hz, H-4), 7.91 ppm (2H, d, ³J = 8.8 Hz, H-2′, 6′); ¹³C NMR (100 MHz, DMSO-d₆): δ 48.68, 52.56, 55.30, 57.99, 69.13, 106.22, 110.44, 112.22, 113.18, 114.49, 124.14, 124.62, 132.83, 146.19, 160.26, 165.12, 166.96, 181.10 ppm; MS (CI): m/z 414.0 (MH⁺, 100). Anal. calcd for C₂₃H₂₇NO₆: C, 66.81; H, 6.58; N, 3.39. Found: C, 66.93; H, 6.73; N, 3.53.

(2Z)-7-{[Bis(2-methoxyethyl)amino]methyl}−2-(3,4-dimethoxybenzylidene)-6-hydroxy-1-benzofuran-3(2H)-one (7c).

Yellow solid (83% yield); mp: 80 – 82^oC; IR (KBr): ν_max 2835, 1687, 1593, 1519, 1322, 1261, 1123, 1021 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.95 (4H, t, ³J = 5.2 Hz, N(CH₂CH₂OMe)₂), 3.32 (6H, s, CH₂OCH₃), 3.59 (4H, t, ³J = 5.2 Hz, N(CH₂CH₂OMe)₂), 3.93, 3.96 (each 3H, 2s, OMe-3ʹ,4ʹ), 4.18 (2H, s, CH₂-7), 6.69 (1H, d, ³J = 8.4 Hz, H-5), 6.74 (1H, s, H-2a), 6.93 (1H, d,³J = 8.4 Hz, H-5ʹ), 7.40 (1H, dd, ³J = 8.4 Hz, ⁴J = 2.0 Hz, H-6ʹ), 7.49 (1H, d, ⁴J = 2.0 Hz, H-2ʹ), 7.59 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 50.23, 53.67, 55.88, 56.07, 58.96, 69.80, 105.09, 111.35, 111.86, 113.60, 113.67, 113.81, 125.24, 125.47, 125.69, 147.12, 149.06, 150.53, 165.56, 167.08, 182.69 ppm; MS (CI): m/z 444.2 (MH⁺, 100). Anal. calcd for C₂₄H₂₉NO₇: C, 65.00; H, 6.59; N, 3.16. Found: C, 64.81; H, 6.82; N, 3.00.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-7-{[bis(2-methoxyethyl)amino]methyl}−6-hydroxy-1-benzofuran-3(2H)-one (7d).

Yellow solid (77% yield); mp: 114 – 116^oC; IR (KBr): ν_max 3421. 1645, 1614, 1564, 1450, 1402, 1257, 1107, 1036 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.97 (4H, t, ³J = 5.3 Hz, N(CH₂CH₂OMe)₂), 3.35 (6H, s, CH₂OCH₃), 3.60 (4H, t, ³J = 5.3 Hz, N(CH₂CH₂OMe)₂), 4.19 (2H, s, CH₂-7), 6.03 (2H, s, OCH₂O), 6.68 (1H, d, ³J = 8.5 Hz, H-5), 6.71 (1H, s, H-2a), 6.87 (1H, d, ³J = 8.0 Hz, H-7ʹ), 7.25 (1H, dd, ³J = 8.0 Hz, ⁴J = 1.8 Hz, H-6ʹ), 7.48 (1H, d, ⁴J = 1.8 Hz, H-4ʹ), 7.59 ppm (1H, d, ³J = 8.5 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 50.32, 53.61, 58.97, 70.03, 101.63, 105.54, 108.93, 110.36, 111.58, 113.56, 113.83, 125.07, 127.08, 127.15, 147.12, 148.26, 148.93, 165.60, 167.42, 182.81 ppm; MS (CI): m/z 428.1 (MH⁺, 100). Anal. calcd for C₂₃H₂₅NO₇: C, 64.63; H, 5.90; N, 3.28. Found: C, 64.78; H, 5.67; N, 3.52.

(2Z)-7-{[Bis(2-methoxyethyl)amino]methyl}−6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (7e).

Yellow solid (88% yield); mp: 119 – 120^oC; IR (KBr): ν_max 2878, 1692, 1602, 1502, 1344, 1185, 1117 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.91 (4H, t, ³J = 5.2 Hz, N(CH₂CH₂OMe)₂), 3.33 (6H, s, CH₂OCH₃), 3.58 (4H, t, ³J = 5.2 Hz, N(CH₂CH₂OMe)₂), 3.92 (3H, s, OMе−4ʹ), 3.95 (6H, s, OMе−3ʹ, 5ʹ), 4.14 (2H, s, CH₂-7), 6.67 (1H, d, ³J = 8.5 Hz, H-5), 6.72 (1H, s, H-2a), 7.15 (2H, s, H-2ʹ, 6ʹ), 7.61 ppm (1H, d, ³J = 8.5 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 50.26, 53.64, 56.17, 58.95, 61.11, 69.69, 105.08, 108.61, 111.60, 113.46, 113.94, 125.37, 128.11, 139.68, 147.67, 153.34, 165.67, 167.25, 182.63 ppm; MS (CI): m/z 474.2 (MH⁺, 100). Anal. calcd for C₂₅H₃₁NO₈: C, 63.41; H, 6.60; N, 2.96. Found: C, 63.30; H, 6.86; N, 3.11.

(2Z)-7-{[Bis(2-methoxyethyl)amino]methyl}−6-hydroxy-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (7f).

Yellow solid (79% yield); mp: 105 – 107^oC; IR (KBr): ν_max 2943, 1691, 1605, 1594, 1303, 1130, 1091, 1041 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.93 (4H, t, ³J = 5.2 Hz, N(CH₂CH₂OMe)₂), 3.35 (6H, s, CH₂OCH₃), 3.59 (4H, t, ³J = 5.2 Hz, N(CH₂CH₂OMe)₂), 3.90, 3.94, 3.97 (each 3H, 3s, OMe-2ʹ, 3ʹ, 4ʹ), 4.15 (2H, s, CH₂-7), 6.66 (1H, d, ³J = 8.4 Hz, H-5), 6.82 (1H, d, ³J = 8.9 Hz, H-5ʹ), 7.20 (1H, s, H-2a), 7.61 (1H, d, ³J = 8.4 Hz, H-4), 7.96 ppm (1H, d, ³J = 8.9 Hz, H-6ʹ); ¹³C NMR (125 MHz, CDCl₃): δ 50.24, 53.71, 56.15, 58.90, 60.97, 61.92, 70.01, 105.35, 105.58, 107.80, 113.59, 113.71, 119.84, 125.00, 126.67, 142.30, 147.74, 153.93, 155.15, 165.46, 167.08, 182.74 ppm; MS (CI): m/z 474.2 (MH⁺, 100). Anal. calcd for C₂₅H₃₁NO₈: C, 63.41; H, 6.60; N, 2.96. Found: C, 63.70; H, 6.36; N, 2.75.

(2Z)-2-Benzylidene-6-hydroxy-7-(piperidin-1-ylmethyl)-1-benzofuran-3(2H)-one (8a).

Yellow solid (85% yield); mp: 187 – 189^oC; IR (KBr): ν_max 2950, 1678, 1608, 1502, 1451, 1371, 1279, 1179, 1117, 1066 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 1.36 – 3.46 (10H, m, piperidine moiety), 4.06 (2H, s, CH₂-7), 6.73 (1H, d, ³J = 8.5 Hz, H-5), 6.79 (1H, s, H-2a), 7.35 – 7.50 (3H, m, H-3ʹ, 4ʹ, 5ʹ), 7.62 (1H, d, ³J = 8.5, H-4), 7.82 (2H, d, ³J = 8.5 Hz, H-2ʹ, 6ʹ), 10.08 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, CDCl₃): δ 23.40, 25.35, 53.43, 53.87, 103.34, 111.49, 113.26, 113.97, 125.74, 129.05, 129.63, 131.21, 132.69, 148.05, 166.21, 168.01, 182.76 ppm; MS (CI): m/z 336.1 (MH⁺, 100). Anal. calcd for C₂₁H₂₁NO₃: C, 75.20; H, 6.31; N, 4.18. Found: C, 75.03; H, 6.09; N, 4.34.

(2Z)-6-Hydroxy-2-(4-methoxybenzylidene)-7-(piperidin-1-ylmethyl)-1-benzofuran-3(2H)-one (8b).

Yellow solid (91% yield); mp: 125 – 126^oC; IR (KBr): ν_max 2935, 1692, 1598, 1509, 14477, 1256, 1187, 1124, 1035 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 1.24 – 1.95, 2.21 – 3.37 (6H, 4H, 2m, piperidine moiety), 3.80 (3H, s, OMe-4ʹ), 3.92 (2H, s, CH₂-7), 6.57 (1H, d, ³J = 8.5 Hz, H-5), 6.69 (1H, s, H-2a), 6.92 (2H, d, ³J = 8.5 Hz, H-3′, 5′), 7.52 (1H, d, ³J = 8.5 Hz, H-4), 7.72 (2H, d, ³J = 8.8 Hz, H-2′, 6′), 11.51 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, CDCl₃): δ 23.64, 25.66, 53.97, 54.16, 55.38, 103.94, 111.41, 113.27, 113.57, 114.48, 124.89, 125.32, 132.89, 146.95, 160.65, 165.52, 167.83, 182.60 ppm; MS (CI): m/z 366.0 (MH⁺, 100). Anal. calcd for C₂₂H₂₃NO₄: C, 72.31; H, 6.34; N, 3.83. Found: C, 72.39; H, 6.62; N, 3.59.

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-(piperidin-1-ylmethyl)-1-benzofuran-3(2H)-one (8c).

Yellow solid (82% yield); mp: 180 – 182^oC; IR (KBr): ν_max 3446, 2937, 2677, 1676, 1616, 1512, 1458, 1269, 1144, 1022 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 1.33– 3.46 (10H, m, piperidine moiety), 3.92 (2H, s, CH₂-7), 3.95, 3.98 (each 3H, 2s, OMe-3ʹ,4ʹ), 6.63 (1H, d, ³J = 8.4 Hz, H-5), 6.76 (1H, s, H-2a), 6.95 (1H, d, ³J = 8.4 Hz, H-5ʹ), 7.40 (1H, dd, ³J = 8.4 Hz, ⁴J = 2.0 Hz, H-6ʹ), 7.51 (1H, d, ⁴J = 2.0 Hz, H-2ʹ), 7.59 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (100 MHz, DMSO-d₆): δ 23.05, 24.85, 52.06, 53.05, 55.29, 55.54, 104.08, 110.17, 110.65, 111.80, 113.39, 114.05, 124.34, 124.92, 125.02, 146.54, 148.55, 149.99, 165.53, 169.26, 180.35 ppm; MS (CI): m/z 396.2 (MH⁺, 100). Anal. calcd for C₂₃H₂₅NO₅: C, 69.86; H, 6.37; N, 3.54. Found: C, 69.97; H, 6.51; N, 3.36.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-(piperidin-1-ylmethyl)-1-benzofuran-3(2H)-one (8d).

Yellow solid (74% yield); mp: 163 – 165^oC; IR (KBr): ν_max 3406, 2949, 1678, 1595, 1448, 1331, 1250, 1132, 1038 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 1.32– 3.56 (10H, m, piperidine moiety), 3.95 (2H, s, CH₂-7), 6.05 (2H, s, OCH₂O), 6.62 (1H, d, ³J = 8.4 Hz, H-5), 6.72 (1H, s, H-2a), 6.88 (1H, d, ³J = 8.1 Hz, H-7ʹ), 7.14 – 7.33 (1H, m, H-6ʹ), 7.46 (1H, d, ⁴J = 1.7 Hz, H-4ʹ) 7.59 (1H, d, ³J = 8.4 Hz, H-4), 10.08 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, DMSO-d₆): δ 23.15, 25.00, 51.88, 53.08, 101.49, 104.46, 108.75, 109.21, 109.68, 109.74, 114.57, 124.19, 126.43, 126.57, 146.87, 147.69, 148.15, 165.91, 170.67, 180.02 ppm; MS (CI): m/z 380.0 (MH⁺, 100). Anal. calcd for C₂₂H₂₁NO₅: C, 69.65; H, 5.58; N, 3.69. Found: C, 69.74; H, 5.47; N, 3.88.

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-(morpholin-4-ylmethyl)-1-benzofuran-3(2H)-one (9c).

Yellow solid (67% yield); mp: 179 – 181^oC; IR (KBr): ν_max 2928, 2836, 1671, 1601,1435, 1264, 1133 cm⁻¹; ¹H NMR (500 MHz, CDCl₃): δ 2.55 – 2.88 (4H, m, N(CH₂CH₂)O), 3.74 – 3.86 (4H, m, N(CH₂CH₂)O), 3.93, 3.96 (each 3H, 2s, OMe-3ʹ,4ʹ), 3.97 (2H, s, CH₂-7), 6.66 (1H, d, ³J = 8.4 Hz, H-5), 6.75 (1H, s, H-2a), 6.94 (1H, d,³J = 8.4 Hz, H-5ʹ), 7.39 (1H, dd, ³J = 8.3 Hz, ⁴J = 1.9 Hz, H-6ʹ), 7.45 (1H, d, ⁴J = 1.9 Hz, H-2ʹ), 7.60 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 53.22, 53.76, 55.84, 56.07, 66.55, 103.40, 103.47, 111.41, 112.28, 113.52, 113.60, 114.02, 125.48, 125.52, 146.92, 149.06, 150.65, 165.58, 166.34, 182.56 ppm; MS (CI): m/z 398.0 (MH⁺, 100). Anal. calcd for C₂₂H₂₃NO₆: C, 66.49; H, 5.83; N, 3.52. Found: C, 66.21; H, 6.08; N, 3.30.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-(morpholin-4-ylmethyl)-1-benzofuran-3(2H)-one (9d).

Yellow solid (59% yield); mp: 189 – 191^oC; IR (KBr): ν_max 3419, 1668, 1599, 1502, 1442, 1254, 1119, 1038 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 2.52 – 2.61 (4H, m, N(CH₂CH₂)O), 3.57 – 3.65 (4H, m, N(CH₂CH₂)O), 3.78 (2H, s, CH₂-7), 6.10 (2H, s, OCH₂O), 6.65 – 6.77 (2H, m, H-2a, 5), 7.03 (1H, d, ³J = 8.1 Hz, H-7ʹ), 7.45 (1H, dd, ³J = 8.1 Hz, ⁴J = 1.7 Hz, H-6ʹ), 7.52 (1H, d, ³J = 8.3 Hz, H-4), 7.58 ppm (1H, d, ⁴J = 1.6 Hz, H-4ʹ); ¹³C NMR (100 MHz, DMSO-d₆): δ 50.80, 52.93, 66.04, 101.60, 106.36, 108.79, 109.79, 110.64, 112.44, 112.74, 124.31, 126.25, 126.95, 146.18, 147.75, 148.51, 165.49, 165.86, 181.24 ppm; MS (CI): m/z 382.3 (MH⁺, 100). Anal. calcd for C₂₁H₁₉NO₆: C, 66.14; H, 5.02; N, 3.67. Found: C, 65.96; H, 5.21; N, 3.90.

(2Z)-6-Hydroxy-7-(morpholin-4-ylmethyl)-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (9e).

Yellow solid (74% yield); mp: 197 – 199^oC; IR (KBr): ν_max 2956, 2835, 1691, 1603, 1504, 1448, 1120 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.48 – 2.93 (4H, m, N(CH₂CH₂)O), 3.78 – 3.87 (4H, m, N(CH₂CH₂)O), 3.91 (3H, s, OMе−4ʹ), 3.94 (6H, s, OMе−3ʹ, 5ʹ), 3.99 (2H, s, CH₂-7),6.63 – 6.78 (2H, m, H-2a, 5), 7.11 (2H, s, H-2ʹ, 6ʹ), 7.62 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (100 MHz, CDCl₃): δ 53.23, 53.53, 56.20, 61.15, 66.38, 103.26, 108.68, 112.14, 113.76, 113.91, 125.85, 127.90, 139.90, 147.46, 153.39, 165.81, 166.43, 182.53 ppm; MS (CI): m/z 428.2 (MH⁺, 100). Anal. calcd for C₂₃H₂₅NO₇: C, 64.63; H, 5.90; N, 3.28. Found: C, 64.37; H, 6.18; N, 3.50.

(2Z)-6-Hydroxy-2-(4-methoxybenzylidene)-7-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-3(2H)-one (10b).

Yellow solid (80% yield); mp: 156 – 158^oC; IR (KBr): ν_max 2801, 1692, 1601, 1509, 1257, 1183, 1129, 1032, 813 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.36 (3H, s, Nʹ-CH₃), 2.39 – 3.15 (8H, m, piperazine moiety), 3.85 (3H, s, OMe-4ʹ), 3.98 (2H, s, CH₂-7), 6.62 (1H, d, ³J = 8.5 Hz, H-5), 6.75 (1H, s, H-2a), 6.97 (2H, d, ³J = 8.9 Hz, H-3′, 5′), 7.58 (1H, d, ³J = 8.5 Hz, H-4), 7.77 (2H, d, ³J = 8.8 Hz, H-2′, 6′), 10.25 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, CDCl₃): δ 45.64, 52.40, 53.39, 54.64, 55.37, 103.93, 111.74, 113.33, 113.75, 114.49, 125.03, 125.18, 132.94, 146.77, 160.72, 165.40, 166.68, 182.62 ppm; MS (CI): m/z 381.2 (MH⁺, 100). Anal. calcd for C₂₂H₂₄N₂O₄: C, 69.46; H, 6.36; N, 7.36. Found: C, 69.73; H, 6.55; N, 7.49.

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-3(2H)-one (10c).

Yellow solid (86% yield); mp: 173 – 175^oC; IR (KBr): ν_max 3423, 2941, 2692, 1662, 1595, 1514, 1452, 1334, 1263, 1128 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.09 – 3.47 (11H, m, piperazine moiety), 3.95 (3H, s) and 3.97 (5H, m, СH₂-7, OMe-3ʹ,4ʹ, ), 6.65 (1H, d, ³J = 8.4 Hz, H-5), 6.78 (1H, s, H-2a), 6.95 (1H, d, ³J = 8.5 Hz, H-5ʹ), 7.38 (1H, dd, ³J = 8.5 Hz, ⁴J = 1,7 Hz, H-6ʹ), 7.55 (1H, d, ⁴J = 1.7 Hz, H-2ʹ), 7.62 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (100 MHz, DMSO-d₆): δ 45.53, 50.86, 52.23, 54.35, 55.34, 55.58, 105.74, 110.79, 111.83, 111.92, 113.24, 113.37, 124.35, 124.81, 125.32, 146.26, 148.58, 150.16, 165.57, 166.78, 180.95 ppm; MS (CI): m/z 411.1 (MH⁺, 100). Anal. calcd for C₂₃H₂₆N₂O₅: C, 67.30; H, 6.38; N, 6.82. Found: C, 67.53; H, 6.54; N, 6.65.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-3(2H)-one (10d).

Yellow solid (69% yield); mp: 190 – 912^oC; IR (KBr): ν_max 3410, 2937, 1689, 1603, 1500, 1446, 1342, 1257, 1188, 1036 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 2.17 (3H, s, Nʹ-CH₃), 2.25 – 2.48 (4H, m) and 2.52 – 2.78 (4 H, m, piperazine ring), 3.84 (2H, s, CH₂-7), 6.11 (2H, s, OCH₂O), 6.65 (1H, d, ³J = 8.5 Hz, H-5), 6.72 (1H, s, H-2a), 7.03 (1H, d, ³J = 8.1 Hz, H-7ʹ), 7.38 – 7.61 ppm (3H, m, H-4, 4ʹ 6ʹ); ¹³C NMR (100 MHz, DMSO-d₆): δ 45.49, 50.77, 52.16, 54.36, 101.58, 105.96, 108.83, 109.81, 110.27, 111.67, 113.34, 124.25, 126.33, 126.84, 146.37, 147.74, 148.43, 165.75, 167.10, 180.90 ppm; MS (CI): m/z 395.1 (MH⁺, 100). Anal. calcd for C₂₂H₂₂N₂O₅: C, 66.99; H, 5.62; N, 7.10. Found: C, 66.84; H, 5.83; N, 6.92.

(2Z)-6-Hydroxy-7-[(4-methylpiperazin-1-yl)methyl]-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (10e).

Yellow solid (82% yield); mp: 201–203^oC; IR (KBr): ν_max 2936, 2810, 1692, 1603, 1422, 1262, 1124, 1048 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.02 – 3.31 (11H, m, piperazine moiety), 3.91 (3H, s, OMе−4ʹ), 3.93 (6H, s, OMе−3ʹ, 5ʹ), 3.94 (2H, s, CH₂-7), 6.66 (1H, d, ³J = 8.5 Hz, H-5), 6.73 (1H, s, H-2a), 7.14 (2H, s, H-2ʹ, 6ʹ), 7.62 ppm (1H, d, ³J = 8.5 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 45.80, 52.95, 53.54, 54.67, 56.06, 61.10, 103.98, 108.54, 111.80, 113.59, 113.61, 125.33, 127.98, 139.69, 147.54, 153.30, 165.49, 166.87, 182.56 ppm; MS (CI): m/z 441.0 (MH⁺, 100). Anal. calcd for C₂₄H₂₈N₂O₆: C, 65.44; H, 6.41; N, 6.36. Found: C, 65.15; H, 6.30; N, 6.15.

(2Z)-6-Hydroxy-7-[(4-methylpiperazin-1-yl)methyl]-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (10f).

Yellow solid (81% yield); mp: 188 – 190^oC; IR (KBr): ν_max 3425, 1635, 1608, 1556, 1456, 1402, 1279, 1093 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 2.17 (3H, s, Nʹ-CH₃), 2.27 – 2.44 (4H, m) and 2.55 – 2.72 (4H, m, piperazine moiety), 3.78 (3H, s) and 3.88 (8H, s, OMe-2ʹ, 3ʹ, 4ʹ, CH₂-7), 6.65 (1H, d, ³J = 8.6 Hz, H-5), 6.88 (1H, s, H-2a), 7.01 (1H, d, ³J = 8.9 Hz, H-5ʹ), 7.52 (1H, d, ³J = 8.6 Hz, H-4), 7.97 ppm (1H, d, ³J = 8.9 Hz, H-6ʹ); ¹³C NMR (100 MHz, DMSO-d₆): δ 45.43, 50.87, 51.99, 54.34, 56.01, 60.42, 61.62, 103.62, 105.67, 108.62, 111.90, 113.19, 118.36, 124.31, 126.16, 141.57, 146.90, 152.80, 154.88, 165.53, 166.80, 180.97 ppm; MS (CI): m/z 441.2 (MH⁺, 100). Anal. calcd for C₂₄H₂₈N₂O₆: C, 65.44; H, 6.41; N, 6.36. Found: C, 65.21; H, 6.67; N, 6.48.

(2Z)-6-Hydroxy-7-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}−2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (11b).

Yellow solid (58% yield); mp: 179 – 181^oC; IR (KBr): ν_max 3410, 2958, 1668, 1605, 1510, 1443, 1254, 1132, 1028 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 2.40 (2H, t, ³J = 6.1 Hz, NʹCH₂CH₂OH), 2.52 – 2.69 (8H, m, CH₂-2ʹʹ,3ʹʹ, 5ʹʹ,6ʹʹ), 3.49 (2H, t, ³J = 6.1 Hz, NʹCH₂CH₂OH), 3.83 (3H, s, OMe-4ʹ), 3.91 (2H, s, СH₂-7), 6.65 (1H, d, ³J = 8.4 Hz, H-5), 6.75 (1H, s, H-2a), 7.07 (2H, d, ³J = 8.7 Hz, H-3ʹ, 5ʹ), 7.51 (1H, d, ³J = 8.4 Hz, H-4), 7.92 ppm (2H, d, ³J = 8.7 Hz, H-2ʹ, 6ʹ); ¹³C NMR (100 MHz, DMSO-d₆): δ 50.97, 52.14, 52.84, 55.33, 58.44, 59.96, 105.57, 110.26, 111.82, 113.27, 114.55, 124.25, 124.70, 132.83, 146.27, 160.22, 165.59, 167.09, 180.96 ppm; MS (CI): m/z 411.0 (MH⁺, 100). Anal. calcd for C₂₃H₂₆N₂O₅: C, 67.30; H, 6.38; N, 6.82. Found: C, 67.51; H, 6.24; N, 6.66.

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}−1-benzofuran-3(2H)-one (11c).

Yellow solid (63% yield); mp: 180 – 182^oC; IR (KBr): ν_max 2947, 1682, 1600, 1513, 1298, 1270, 1139, 1123, 1039 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.08 – 3.36 (10H, m, NʹCH₂CH₂OH and piperazine ring), 3.65 (2H, t, ³J = 5.4 Hz, NʹCH₂CH₂OH), 3.95, 3.98 (each 3H, 2s, OMe-3ʹ,4ʹ), 3.97 (2H, s, CH₂-7), 6.65 (1H, d, ³J = 8.4 Hz, H-5), 6.78 (1H, s, H-2a), 6.95 (1H, d,³J = 8.4 Hz, H-5ʹ), 7.41 (1H, dd, ³J = 8.4 Hz, ⁴J = 2.0 Hz, H-6ʹ), 7.50 (1H, d, ⁴J = 2.0 Hz, H-2ʹ), 7.62 ppm (1H, d, ³J = 8.4 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 52.68, 52.87, 53.56, 55.88, 56.10, 57.93, 59.33, 103.93, 111.43, 112.19, 113.52, 113.63, 113.92, 125.31, 125.54, 125.56, 147.02, 149.08, 150.64, 165.45, 166.66, 182.66 ppm; MS (CI): m/z 441.1 (MH⁺, 100). Anal. calcd for C₂₄H₂₈N₂O₆: C, 65.44; H, 6.41; N, 6.36. Found: C, 65.72; H, 6.70; N, 6.09.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}−1-benzofuran-3(2H)-one (11d).

Yellow solid (55% yield); mp: 162 – 164^oC; IR (KBr): ν_max 2944, 1690, 1608, 1499, 1451, 1291, 1262, 1115, 1042 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.47 – 2.91 (10H, m, NʹCH₂CH₂OH and piperazine ring), 3.64 (2H, t, ³J = 5.3 Hz, NʹCH₂CH₂OH), 3.96 (2H, s, CH₂-7), 6.01 (2H, s, OCH₂O), 6.60 (1H, d, ³J = 8.3 Hz, H-5), 6.68 (1H, s, H-2a), 6.84 (1H, d, ³J = 8.0 Hz, H-7ʹ), 7.19 – 7.27 (1H, m, H-6ʹ), 7.40 (1H, d, ⁴J = 1.6 Hz, H-4ʹ), 7.56 ppm (1H, d, ³J = 8.3 Hz, H-4); ¹³C NMR (100 MHz, CDCl₃): δ 52.65, 52.69, 53.51, 57.90, 59.28, 101.64, 104.04, 108.93, 110.32, 111.93, 113.55, 113.75, 125.21, 126.83, 127.20, 146.88, 148.23, 149.02, 165.48, 166.87, 182.66 ppm; MS (CI): m/z 425.2 (MH⁺, 100). Anal. calcd for C₂₃H₂₄N₂O₆: C, 65.08; H, 5.70; N, 6.60. Found: C, 65.29; H, 5.93; N, 6.88.

(2Z)-6-Hydroxy-7-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}−2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (11e).

Yellow solid (68% yield); mp: 187 – 189^oC; IR (KBr): ν_max 2939, 2820, 1688, 1602, 1451, 1309, 1262, 1133, 1120 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.39 – 3.08 (10H, m, NʹCH₂CH₂OH and piperazine ring), 3.66 (2H, t, ³J = 5.4 Hz, NʹCH₂CH₂OH), 3.93 (3H, s, OMе−4ʹ), 3.95 (8H, s, CH₂-7, OMе−3ʹ, 5ʹ), 6.67 (1H, d, ³J = 8.5 Hz, H-5), 6.74 (1H, s, H-2a), 7.15 (2H, s, H-2ʹ, 6ʹ), 7.63 ppm (1H, d, ³J = 8.5 Hz, H-4); ¹³C NMR (100 MHz, CDCl₃): δ 52.59, 53.06, 53.50, 56.12, 58.03, 59.29, 61.10, 103.93, 108.59, 108.67, 111.85, 113.62, 125.35, 127.97, 139.72, 147.53, 153.31, 165.50, 166.85, 182.57 ppm; MS (CI): m/z 471.2 (MH⁺, 100). Anal. calcd for C₂₅H₃₀N₂O₇: C, 63.82; H, 6.43; N, 5.95. Found: C, 64.10; H, 6.71; N, 6.13.

General procedure for the synthesis of diacetates 12.

A mixture of a Mannich base 3a-3d (2 mmol) and 200 mg (2 mmol) of potassium acetate in 5 mL of acetic anhydride was refluxed for 5 min and cooled to room temperature. The mixture was diluted with water to afford a precipitate of 12a-12d, that was recrystallized from acetonitrile-water.

[(2Z)-6-(Acetyloxy)-2-benzylidene-3-oxo-2,3-dihydro-1-benzofuran-7-yl]methyl acetate (12a).

Yellow solid (93% yield); mp: 145–147^oC; IR (KBr): ν_max 1770, 1738, 1706, 1605, 1434, 1255, 1188, 1129 cm⁻¹; ; ¹H NMR (500 MHz, CDCl₃): δ 2.09 (3H, s, CH₃COO-6), 2.39 (3H, s, CH₃COOCH₂-7), 5.36 (2H, s, CH₂-7), 6.93 (1H, s, H-2a), 7.00 (1H, d, ³J = 8.3 Hz, H-5), 7.39 – 7.51 (3H, m, H-3ʹ, 4ʹ, 5ʹ), 7.82 (1H, d, ³J = 8.4 Hz, H-4), 7.91 ppm (2H, d, ³J = 8.3 Hz, H-2ʹ, 6ʹ); ¹³C NMR (125 MHz, CDCl₃): δ 20.81, 20.94, 54.73, 114.02, 114.44, 118.87, 119.77, 125.70, 129.16, 130.34, 131.80, 132.15, 147.22, 156.25, 165.79, 168.60, 170.63, 183.39 ppm; MS (CI): m/z 353.0 (MH⁺, 100). Anal. calcd for C₂₀H₁₆O₆: C, 68.18; H, 4.58. Found: C, 68.33; H, 4.45.

[(2Z)-6-(Acetyloxy)-2-(4-methoxybenzylidene)-3-oxo-2,3-dihydro-1-benzofuran-7-yl]methyl acetate (12b).

Yellow solid (81% yield); mp: 135–137^oC; IR (KBr): ν_max 2936, 2840, 1771, 1735, 1650, 1601, 1512, 1431, 1256, 1195, 1134 cm⁻¹; ¹H NMR (400 MHz, CDCl₃) δ 2.09 (3H, s, CH₃COO-6), 2.39 (3H, s, CH₃COOCH₂-7), 3.88 (3H, s, OMe-4ʹ), 5.36 (2H, s, CH₂-7), 6.92 (1H, s, H-2a), 6.96 – 7.03 (3H, m, H-5, 3′, 5′), 7.82 (1H, d, ³J = 8.3 Hz, H-4), 7.88 ppm (2H, d, ³J = 8.8 Hz, H-2′, 6′); ¹³C NMR (100 MHz, CDCl₃): δ 20.77, 20.87, 54.61, 55.45, 114.10, 114.27, 114.67, 118.51, 119.97, 124.71, 125.49, 133.63, 146.07, 155.81, 161.35, 165.26, 168.60, 170.58, 183.02 ppm; MS (CI): m/z 383.2 (MH⁺, 100). Anal. calcd for C₂₁H₁₈O₇: C, 65.97; H, 4.75. Found: C, 66.11; H, 5.03.

[(2Z)-6-(Acetyloxy)-2-(3,4-dimethoxybenzylidene)-3-oxo-2,3-dihydro-1-benzofuran-7-yl]methyl acetate (12c).

Yellow solid (91% yield); mp: 190–192^oC; IR (KBr): ν_max 2963, 2845, 1772, 1736, 1647, 1595, 1514, 1259, 1184, 1127, 1065, 1021 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.06 (3H, s, CH₃COO-6), 2.38 (3H, s, CH₃COOCH₂-7), 3.94, 3.96 (each 3H, 2s, OMe-3ʹ, 4ʹ), 5.32 (2H, s, CH₂-7), 6.89 (1H, s, H-2a), 6.94 (1H, d, ³J = 8.3 Hz, H-5), 6.98 (1H, d,³J = 8.4 Hz, H-5ʹ), 7.35 – 7.47 (1H, m, H-6ʹ), 7.62 (1H, d, ⁴J = 2.0 Hz, H-2ʹ), 7.81 ppm (1H, d, ³J = 8.3 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 20.81, 20.97, 54.68, 55.92, 56.10, 111.32, 113.56, 114.06, 114.68, 118.74, 120.00, 125.08, 125.70, 126.52, 146.22, 149.29, 151.26, 156.07, 165.25, 168.72, 170.59, 183.00 ppm; MS (CI): m/z 413.2 (MH⁺, 100). Anal. calcd for C₂₂H₂₀O₈: C, 64.08; H, 4.89. Found: C, 63.92; H, 4.60.

[(2Z)-6-(Acetyloxy)-2-(1,3-benzodioxol-5-ylmethylene)-3-oxo-2,3-dihydro-1-benzofuran-7-yl]methyl acetate (12d).

Yellow solid (88% yield); mp: 170–172^oC; IR (KBr): ν_max 1765, 1737, 1704, 1649, 1611, 1257, 1200, 1031 cm⁻¹; ¹H NMR (400 MHz, CDCl₃): δ 2.09 (3H, s, CH₃COO-6), 2.39 (3H, s, CH₃COOCH₂-7), 5.35 (2H, s, CH₂-7), 6.05 (2H, s, OCH₂O), 6.86 (1H, s, H-2a), 6.89 (1H, d, ³J = 8.3 Hz, H-5), 6.99 (1H, d, ³J = 8.3 Hz, H-7ʹ), 7.29 – 7.35 (1H, m, H-6ʹ), 7.58 (1H, d, ⁴J = 1.6 Hz, H-4ʹ), 7.81 ppm (1H, d, ³J = 8.3 Hz, H-4); ¹³C NMR (125 MHz, CDCl₃): δ 20.87, 20.99, 54.71, 101.85, 109.03, 110.75, 114.34, 114.46, 118.74, 119.98, 125.61, 126.42, 128.12, 146.20, 148.51, 149.74, 155.95, 165.36, 168.74, 183.12 ppm; MS (CI): m/z 397.0 (MH⁺, 100). Anal. calcd for C₂₁H₁₆O₈: C, 63.64; H, 4.07. Found: C, 63.87; H, 4.22.

General procedure for the synthesis of 7-methoxymethyl-6-hydroxyaurones 13a-13d.

A mixture of diacetate 12a-12d (2 mmol) and 0.1 mL of concentrated hydrochloric acid in 10 mL of methanol was refluxed for 16–24 h. The mixture was cooled and diluted with water, and the resulting precipitate was collected by filtration. The products were purified by chromatography using 1:20 methanol-dichloromethane.

(2Z)-2-Benzylidene-6-hydroxy-7-(methoxymethyl)-1-benzofuran-3(2H)-one (13a).

Yellow solid (43% yield); mp: 332–333^oC; IR (KBr): ν_max 2893, 1677, 1583, 1442, 1305, 1284, 1135, 1061 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.34 (3H, s, CH₃OCH₂-7), 4.59 (2H, s, CH₂-7), 6.76 – 6.86 (2H, m, H-2a, 5), 7.41 – 7.55 (3H, m, H-3ʹ, 4ʹ, 5ʹ), 7.61 (1H, d, ³J = 8.5 Hz, H-4), 7.95 – 8.01 (2H, d, ³J = 8.8 Hz, H-2ʹ, 6ʹ), 11.34 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, DMSO-d₆): δ 57.63, 61.60, 108.36, 110.43, 112.47, 112.61, 125.49, 129.02, 129.68, 131.08, 132.17, 147.37, 164.88, 166.86, 181.70 ppm; MS (CI): m/z 251.0 (MH⁺−32, 100). Anal. calcd for C₁₇H₁₄O₄: C, 72.33; H, 5.00. Found: C, 72.46; H, 5.19.

(2Z)-6-Hydroxy-2-(4-methoxybenzylidene)-7-(methoxymethyl)-1-benzofuran-3(2H)-one (13b).

Yellow solid (53% yield); mp: 185–187cels ; IR (KBr): ν_max 3097, 2926, 1674, 1600, 1446, 1287, 1263, 1137, 1064 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.33 (3H, s, CH₃OCH₂-7), 3.83 (3H, s, OMe-4ʹ), 4.59 (2H, s, CH₂-7), 6.76 – 6.84 (2H, m, H-2a, 5), 7.09 (2H, d, ³J = 8.5 Hz, H-3′, 5′), 7.59 (1H, d, ³J = 8.4 Hz, H-4), 7.94 (2H, d, ³J = 8.5 Hz, H-2′, 6′), 11.25 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, DMSO-d₆): δ 55.37, 57.62, 61.62, 108.27, 110.86, 112.44, 112.78, 114.67, 124.66, 125.28, 132.99, 146.16, 160.49, 164.54, 166.50, 181.49 ppm; MS (CI): m/z 313.2 (MH⁺, 100). Anal. calcd for C18H16O5: C, 69.22; H, 5.16. Found: C, C, 69.48; H, 5.41.

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-(methoxymethyl)-1-benzofuran-3(2H)-one (13c).

Yellow solid (69% yield); mp: 225 – 227^oC; IR (KBr): ν_max 2917, 1664, 1605, 1581, 1515, 1303, 1303, 1274, 1136 cm⁻¹; ¹H NMR (500 MHz, DMSO-d₆): δ 3.30 (3H, s, CH₃OCH₂-7), 3.82, 3.86 (each 3H, 2s, OMe-3ʹ,4ʹ), 4.57 (2H, s, CH₂-7), 6.77 (1H, s, H-2a), 6.80 (1H, d, ³J = 8.4 Hz, H-5), 7.07 (1H, d,³J = 8.4 Hz, H-5ʹ), 7.48 (1H, dd, ³J = 8.3 Hz, ⁴J = 1.9 Hz, H-6ʹ), 7.58 (1H, d, ³J = 8.4 Hz, H-4), 7.69 (1H, d, ⁴J = 1.9 Hz, H-2ʹ), 11.24 ppm (1H, br. s, OH-6); ¹³C NMR (125 MHz, DMSO-d₆): δ 55.21, 55.56, 57.54, 61.72, 108.20, 111.28, 111.84, 112.42, 112.80, 113.32, 124.80, 125.25, 125.57, 146.15, 148.70, 150.37, 164.52, 166.42, 181.40 ppm; MS (CI): m/z 343.2 (MH⁺, 100). Anal. calcd for C₁₉H₁₈O₆: C, 66.66; H, 5.30. Found: C, 66.90; H, 5.48.

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-(methoxymethyl)-1-benzofuran-3(2H)-one (13d).

Yellow solid (54% yield); mp: 310–311^oC; IR (KBr): ν_max 2900, 1671, 1603, 1442, 1295, 1258, 1147, 1033 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.32 (3H, s, CH₃OCH₂-7), 4.56 (2H, s, CH₂-7), 6.11 (2H, s, OCH₂O), 6.76 (1H, s, H-2a), 6.79 (1H, d, ³J = 8.5 Hz, H-5), 7.04 (1H, d, ³J = 8.1 Hz, H-7ʹ), 7.43 – 7.50 (1H, m, H-6ʹ), 7.53 – 7.61 (2H, m, H-4, 4ʹ), 11.26 ppm (1H, br. s, OH-6); ¹³C NMR (100 MHz, DMSO-d₆): δ 57.66, 61.77, 101.68, 108.28, 108.93, 109.87, 110.92, 112.48, 112.71, 125.27, 126.29, 127.10, 146.22, 147.87, 148.69, 164.50, 166.49, 181.43 ppm; MS (CI): m/z 327.0 (MH⁺, 100). Anal. calcd for C₁₈H₁₄O₆: C, 66.26; H, 4.32. Found: C, 66.03; H, 4.58.

Cell Proliferation Assay

Prostate cancer PC-3 cells (American Type Culture Collection, Manassas, VA 20110 USA) were cultured in DMEM/F-12 HAM Mixture (Sigma D8437) containing 10% Fetal Bovine Serum (Atlanta Biological S11150). Cells (3.5×10⁴ cells per well) were split into 12-well plates. After 24 h, 10mM of each compound were added to each well. DMSO was used as a control. Each experiment was done in triplicate. Cell viability and number were analyzed using the Vi-Cell XR Cell Viability Analyzer (Beckman Coulter). Compounds were tested in triplicate at concentrations of 100 nM, 300 nM, 1 μM, 3 μM and 10 μM, and IC₅₀ values were calculated using GraphPad Prism6 (GraphPad Software, La Jolla, CA 92037 USA)

Supplementary Material

NIHMS1801848-supplement-Supplementary_Material.pdf^{(18.5MB, pdf)}

Figure 1. — 6-Hydroxybenzofuran-3-(2H)-one 1 and 6-hydroxyaurones 2.

Acknowledgments

CL and DSW were supported by NCI CA172379. CL and DSW have partial ownership of a new-start company, Epionc, Inc., that seeks to develop these compounds as commercial agents. CL and DSW disclosed this information and complied with requirements to mitigate any potential conflicts of interest in accord with University of Kentucky policy. DSW was also supported by the Office of the Dean of the College of Medicine, by the Center for Pharmaceutical Research and Innovation in the College of Pharmacy, and by NIH Grant Number P30 GM110787 from the National Institute of General Medical Sciences to L. Hersh, PI. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH or the NIGMS. DSW was also supported by the Office of the Assistant Secretary of Defense for Health Affairs, through the Prostate Cancer Research Program (PCRP) under Award No. W81XWH-16–1-0635. Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the Department of Defense. JLM and MVF were supported by NCI R21 CA205108, PCRP W81XWH-16–1-0633, and NCI P30 CA016056.

Footnotes

^†

Electronic Supplementary Information (ESI) available: Copies of NMR data for synthesized compounds are available online. See DOI:

References and notes:

1.Haudecoeur R; Boumendjel A Curr. Med. Chem 2012, 19, 2861–2875. [DOI] [PubMed] [Google Scholar]
2.Boumendjel A Curr. Med. Chem 2003, 10, 2621–2630. [DOI] [PubMed] [Google Scholar]
3.Sim HM; Loh KY; Yeo WK; Lee CY; Go ML; Yeo WK ChemMedChem 2011, 6, 713 – 724. [DOI] [PubMed] [Google Scholar]
4.Horváti K; Bacsa B; Szabó N; Dávid S; Mező G; Grolmusz V; Vértessy B; Hudecz F; Bősze S Bioconjugate Chem. 2012, 23, 900–907. [DOI] [PubMed] [Google Scholar]
5.Schoepfer J; Fretz H; Chaudhuri B; Muller L; Seeber E; Meijer L; Lozach O; Vangrevelinghe E; Furet PJ Med. Chem 2002, 45, 1741–1747. [DOI] [PubMed] [Google Scholar]
6.Carrasco MP; Newton AS; Gonçalves L; Góis A; Machado M; Gut J; Nogueira F; Hänscheid T; Guedes RC; dos Santos DJVA; Rosenthal PJ; Moreira R Eur. J. Med. Chem 2014, 80, 523–534. [DOI] [PubMed] [Google Scholar]
7.Sheng R; Xu Y; Hu C; Zhang J; Lin X; Li J; Yang B; He Q; Hu Y Eur. J. Med. Chem 2009, 44, 7–17. [DOI] [PubMed] [Google Scholar]
8.Nakano H; Saito N; Parker L; Tada Y; Abe M; Tsuganezawa K; Yokoyama S; Tanaka A; Kojima H; Okabe T; Nagano TJ Med. Chem 2012, 55, 5151–5164. [DOI] [PubMed] [Google Scholar]
9.Choi H; Park HJ; Shin JC; Ko HS; Lee JK; Lee S; Park H; Hong S Bioorg. Med. Chem. Lett 2012, 22, 2195–2199. [DOI] [PubMed] [Google Scholar]
10.Lewin G; Aubert G; Thoret S; Dubois J; Cresteil T Bioorg. Med. Chem 2012, 20, 1231–1239. [DOI] [PubMed] [Google Scholar]
11.Liu T; Xu Z; He Q; Chen Y; Yang B; Hu Y Bioorg. Med. Chem. Lett 2007, 17, 278 – 281. [DOI] [PubMed] [Google Scholar]
12.Zhang S; Ma J; Bao Y; Yang P; Zou L; Li K; Sun X Bioorg. Med. Chem 2008, 16, 7128–7133. [DOI] [PubMed] [Google Scholar]
13.Gao M; Wang M; Miller KD; Zheng Q-H Bioorg. Med. Chem. Lett 2013, 23, 4342–4346. [DOI] [PubMed] [Google Scholar]
14.Bandgar BP; Patil SA; Korbad BL; Biradar SC; Nile SN; Khobragade CN Eur. J. Med. Chem 2010, 45, 3223–3227. [DOI] [PubMed] [Google Scholar]
15.Lipeeva AV; Shul’ts EE; Shakirov MM; Bagryanskaya IY; Tolstikov GA Russ. J. Org. Chem 2013, 49, 403–411. [Google Scholar]
16.Nguyen TB; Wang Q; Guéritte F Eur. J. Org. Chem 2011, 2011, 7076–7079. [Google Scholar]
17.Frasinyuk MS; Bondarenko SP; Khilya VP; Liu C; Watt DS; Sviripa VM Org. Biomol. Chem 2015, 13, 1053–1067. [DOI] [PMC free article] [PubMed] [Google Scholar]
18.MacLeod PD; Li Z; Li C-J Tetrahedron 2010, 66, 1045–1050. [Google Scholar]
19.Cimarelli C; Fratoni D; Mazzanti A; Palmieri G Eur. J. Org. Chem 2011, 2011, 2094–2100. [Google Scholar]
20.Nguyen TB; Lozach O; Surpateanu G; Wang Q; Retailleau P; Iorga BI; Meijer L; Guéritte FJ Med. Chem 2012, 55, 2811–2819. [DOI] [PubMed] [Google Scholar]
21.Mrug GP; Bondarenko SP; Khilya VP; Frasinyuk MS Chem. Nat. Compd 2013, 49, 235–241. [Google Scholar]
22.Bondarenko SP; Levenets AV; Frasinyuk MS; Khilya VP Chem. Nat. Compd 2003, 39, 271–275. [Google Scholar]

Associated Data

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

Supplementary Materials

Supplementary Material

NIHMS1801848-supplement-Supplementary_Material.pdf^{(18.5MB, pdf)}

[R1] 1.Haudecoeur R; Boumendjel A Curr. Med. Chem 2012, 19, 2861–2875. [DOI] [PubMed] [Google Scholar]

[R2] 2.Boumendjel A Curr. Med. Chem 2003, 10, 2621–2630. [DOI] [PubMed] [Google Scholar]

[R3] 3.Sim HM; Loh KY; Yeo WK; Lee CY; Go ML; Yeo WK ChemMedChem 2011, 6, 713 – 724. [DOI] [PubMed] [Google Scholar]

[R4] 4.Horváti K; Bacsa B; Szabó N; Dávid S; Mező G; Grolmusz V; Vértessy B; Hudecz F; Bősze S Bioconjugate Chem. 2012, 23, 900–907. [DOI] [PubMed] [Google Scholar]

[R5] 5.Schoepfer J; Fretz H; Chaudhuri B; Muller L; Seeber E; Meijer L; Lozach O; Vangrevelinghe E; Furet PJ Med. Chem 2002, 45, 1741–1747. [DOI] [PubMed] [Google Scholar]

[R6] 6.Carrasco MP; Newton AS; Gonçalves L; Góis A; Machado M; Gut J; Nogueira F; Hänscheid T; Guedes RC; dos Santos DJVA; Rosenthal PJ; Moreira R Eur. J. Med. Chem 2014, 80, 523–534. [DOI] [PubMed] [Google Scholar]

[R7] 7.Sheng R; Xu Y; Hu C; Zhang J; Lin X; Li J; Yang B; He Q; Hu Y Eur. J. Med. Chem 2009, 44, 7–17. [DOI] [PubMed] [Google Scholar]

[R8] 8.Nakano H; Saito N; Parker L; Tada Y; Abe M; Tsuganezawa K; Yokoyama S; Tanaka A; Kojima H; Okabe T; Nagano TJ Med. Chem 2012, 55, 5151–5164. [DOI] [PubMed] [Google Scholar]

[R9] 9.Choi H; Park HJ; Shin JC; Ko HS; Lee JK; Lee S; Park H; Hong S Bioorg. Med. Chem. Lett 2012, 22, 2195–2199. [DOI] [PubMed] [Google Scholar]

[R10] 10.Lewin G; Aubert G; Thoret S; Dubois J; Cresteil T Bioorg. Med. Chem 2012, 20, 1231–1239. [DOI] [PubMed] [Google Scholar]

[R11] 11.Liu T; Xu Z; He Q; Chen Y; Yang B; Hu Y Bioorg. Med. Chem. Lett 2007, 17, 278 – 281. [DOI] [PubMed] [Google Scholar]

[R12] 12.Zhang S; Ma J; Bao Y; Yang P; Zou L; Li K; Sun X Bioorg. Med. Chem 2008, 16, 7128–7133. [DOI] [PubMed] [Google Scholar]

[R13] 13.Gao M; Wang M; Miller KD; Zheng Q-H Bioorg. Med. Chem. Lett 2013, 23, 4342–4346. [DOI] [PubMed] [Google Scholar]

[R14] 14.Bandgar BP; Patil SA; Korbad BL; Biradar SC; Nile SN; Khobragade CN Eur. J. Med. Chem 2010, 45, 3223–3227. [DOI] [PubMed] [Google Scholar]

[R15] 15.Lipeeva AV; Shul’ts EE; Shakirov MM; Bagryanskaya IY; Tolstikov GA Russ. J. Org. Chem 2013, 49, 403–411. [Google Scholar]

[R16] 16.Nguyen TB; Wang Q; Guéritte F Eur. J. Org. Chem 2011, 2011, 7076–7079. [Google Scholar]

[R17] 17.Frasinyuk MS; Bondarenko SP; Khilya VP; Liu C; Watt DS; Sviripa VM Org. Biomol. Chem 2015, 13, 1053–1067. [DOI] [PMC free article] [PubMed] [Google Scholar]

[R18] 18.MacLeod PD; Li Z; Li C-J Tetrahedron 2010, 66, 1045–1050. [Google Scholar]

[R19] 19.Cimarelli C; Fratoni D; Mazzanti A; Palmieri G Eur. J. Org. Chem 2011, 2011, 2094–2100. [Google Scholar]

[R20] 20.Nguyen TB; Lozach O; Surpateanu G; Wang Q; Retailleau P; Iorga BI; Meijer L; Guéritte FJ Med. Chem 2012, 55, 2811–2819. [DOI] [PubMed] [Google Scholar]

[R21] 21.Mrug GP; Bondarenko SP; Khilya VP; Frasinyuk MS Chem. Nat. Compd 2013, 49, 235–241. [Google Scholar]

[R22] 22.Bondarenko SP; Levenets AV; Frasinyuk MS; Khilya VP Chem. Nat. Compd 2003, 39, 271–275. [Google Scholar]

PERMALINK

Efficient Synthesis of Aurone Mannich Bases and Evaluation of their Antineoplastic Activity in PC-3 Prostate Cancer Cells

Antonina V Popova

Mykhaylo S Frasinyuk

Svitlana P Bondarenko

Wen Zhang

Yanqi Xie

Zachary M Martin

Xianfeng Cai

Michael V Fiandalo

James L Mohler

Chunming Liu

David S Watt

Vitaliy M Sviripa

Abstract

Graphical Abstract

Introduction

Results and Discussion

Scheme 1.

Scheme 2.

Table 1.

Conclusions

Experimental

Chemistry

General procedure for the synthesis of 6-hydroxyaurones 2a-2f.

(2Z)-2-Benzylidene-6-hydroxy-1-benzofuran-3(2H)-one (2a).

(2Z)-6-Hydroxy-2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (2b).

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-1-benzofuran-3(2H)-one (2c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-1-benzofuran-3(2H)-one (2d).

(2Z)-6-Hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (2e).

(2Z)-6-Hydroxy-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (2f).

General procedure for the synthesis of Mannich bases 3–11.

(2Z)-2-Benzylidene-7-[(dimethylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (3a).

(2Z)-7-[(Dimethylamino)methyl]-6-hydroxy-2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (3b).

(2Z)-2-(3,4-Dimethoxybenzylidene)-7-[(dimethylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (3c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-7-[(dimethylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (3d).

(2Z)-7-[(Dimethylamino)methyl]-6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (3e).

(2Z)-7-[(Dimethylamino)methyl]-6-hydroxy-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (3f).

(2Z)-7-{[Butyl(methyl)amino]methyl}−6-hydroxy-2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (4b).

(2Z)-7-{[Butyl(methyl)amino]methyl}−2-(3,4-dimethoxybenzylidene)-6-hydroxy-1-benzofuran-3(2H)-one (4c).

(2Z)-7-{[Butyl(methyl)amino]methyl}−6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (4e).

(2Z)-7-{[Benzyl(methyl)amino]methyl}−2-(3,4-dimethoxybenzylidene)-6-hydroxy-1-benzofuran-3(2H)-one (5c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-7-{[benzyl(methyl)amino]methyl}−6-hydroxy-1-benzofuran-3(2H)-one (5d).

(2Z)-7-{[Benzyl(methyl)amino]methyl}−6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (5e).

(2Z)-7-{[Benzyl(methyl)amino]methyl}−6-hydroxy-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (5f).

(2Z)-2-(3,4-Dimethoxybenzylidene)-7-[(dipropylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (6c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-7-[(dipropylamino)methyl]-6-hydroxy-1-benzofuran-3(2H)-one (6d).

(2Z)-7-[(Dipropylamino)methyl]-6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (6e).

(2Z)-2-Benzylidene-7-{[bis(2-methoxyethyl)amino]methyl}−6-hydroxy-1-benzofuran-3(2H)-one (7a).

(2Z)-7-{[Bis(2-methoxyethyl)amino]methyl}−6-hydroxy-2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (7b).

(2Z)-7-{[Bis(2-methoxyethyl)amino]methyl}−2-(3,4-dimethoxybenzylidene)-6-hydroxy-1-benzofuran-3(2H)-one (7c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-7-{[bis(2-methoxyethyl)amino]methyl}−6-hydroxy-1-benzofuran-3(2H)-one (7d).

(2Z)-7-{[Bis(2-methoxyethyl)amino]methyl}−6-hydroxy-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (7e).

(2Z)-7-{[Bis(2-methoxyethyl)amino]methyl}−6-hydroxy-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (7f).

(2Z)-2-Benzylidene-6-hydroxy-7-(piperidin-1-ylmethyl)-1-benzofuran-3(2H)-one (8a).

(2Z)-6-Hydroxy-2-(4-methoxybenzylidene)-7-(piperidin-1-ylmethyl)-1-benzofuran-3(2H)-one (8b).

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-(piperidin-1-ylmethyl)-1-benzofuran-3(2H)-one (8c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-(piperidin-1-ylmethyl)-1-benzofuran-3(2H)-one (8d).

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-(morpholin-4-ylmethyl)-1-benzofuran-3(2H)-one (9c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-(morpholin-4-ylmethyl)-1-benzofuran-3(2H)-one (9d).

(2Z)-6-Hydroxy-7-(morpholin-4-ylmethyl)-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (9e).

(2Z)-6-Hydroxy-2-(4-methoxybenzylidene)-7-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-3(2H)-one (10b).

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-3(2H)-one (10c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-[(4-methylpiperazin-1-yl)methyl]-1-benzofuran-3(2H)-one (10d).

(2Z)-6-Hydroxy-7-[(4-methylpiperazin-1-yl)methyl]-2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (10e).

(2Z)-6-Hydroxy-7-[(4-methylpiperazin-1-yl)methyl]-2-(2,3,4-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (10f).

(2Z)-6-Hydroxy-7-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}−2-(4-methoxybenzylidene)-1-benzofuran-3(2H)-one (11b).

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}−1-benzofuran-3(2H)-one (11c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}−1-benzofuran-3(2H)-one (11d).

(2Z)-6-Hydroxy-7-{[4-(2-hydroxyethyl)piperazin-1-yl]methyl}−2-(3,4,5-trimethoxybenzylidene)-1-benzofuran-3(2H)-one (11e).

General procedure for the synthesis of diacetates 12.

[(2Z)-6-(Acetyloxy)-2-benzylidene-3-oxo-2,3-dihydro-1-benzofuran-7-yl]methyl acetate (12a).

[(2Z)-6-(Acetyloxy)-2-(4-methoxybenzylidene)-3-oxo-2,3-dihydro-1-benzofuran-7-yl]methyl acetate (12b).

[(2Z)-6-(Acetyloxy)-2-(3,4-dimethoxybenzylidene)-3-oxo-2,3-dihydro-1-benzofuran-7-yl]methyl acetate (12c).

[(2Z)-6-(Acetyloxy)-2-(1,3-benzodioxol-5-ylmethylene)-3-oxo-2,3-dihydro-1-benzofuran-7-yl]methyl acetate (12d).

General procedure for the synthesis of 7-methoxymethyl-6-hydroxyaurones 13a-13d.

(2Z)-2-Benzylidene-6-hydroxy-7-(methoxymethyl)-1-benzofuran-3(2H)-one (13a).

(2Z)-6-Hydroxy-2-(4-methoxybenzylidene)-7-(methoxymethyl)-1-benzofuran-3(2H)-one (13b).

(2Z)-2-(3,4-Dimethoxybenzylidene)-6-hydroxy-7-(methoxymethyl)-1-benzofuran-3(2H)-one (13c).

(2Z)-2-(1,3-Benzodioxol-5-ylmethylene)-6-hydroxy-7-(methoxymethyl)-1-benzofuran-3(2H)-one (13d).