Antitumour indolequinones: synthesis and activity against human pancreatic cancer cells

Abstract

An important determinant of the growth inhibitory activity of indolequinones against pancreatic cancer cells is substitution on the 2-position with 2-unsubstituted derivatives being markedly more potent. A series of indolequinones bearing a range of substituents on nitrogen and at the indolylcarbinyl position was prepared by copper(II)-mediated reaction of bromoquinones and enamines, followed by functional group interconversions. The compounds were then assayed for their ability to inhibit the growth of pancreatic cancer cells. The pK_a of the leaving group at the 3-position was shown to influence growth inhibitory activity that is consistent with the proposed mechanism of action of reduction, loss of leaving group and formation of a reactive iminium species. Substitutions on the indole nitrogen were well tolerated with little influence on growth inhibitory activity while substitutions at the 5- and 6- positions larger than methoxy led to decreased activity. The studies presented define the range of substitutions of 2-unsubstituted indolequinones required for optimal growth inhibitory activity.

Introduction

Compounds containing the indolequinone core structure often possess powerful biological activity. Examples include the well known natural product mitomycin C (MMC) used clinically for the treatment of solid tumours,¹ the synthetic MMC analogue EO9 (apaziquone, EOquin) currently being trialled as a treatment for bladder cancer,^{2, 3} and the antitumour zyzzyanone B and related pyrroloindolequinone natural products (Figure 1).⁴ Hence indolequinones have attracted considerable interest in the anticancer arena not only as cytotoxins, but also as bioreductively activated prodrugs.^5–8 In continuation of our studies on the synthesis and biology of indolequinones, we investigated a number of relatively simple tri- and tetra-substituted derivatives initially evaluating their cytotoxicity and also their metabolism by quinone reductase enzymes.^9–16

Figure 1.

Indolequinones with antitumour properties.

In terms of cytotoxicity towards cancer cell lines, it became apparent that the 2-unsubsituted indolequinones were the most potent, and therefore we initiated a more detailed study on the 5- and 6-methoxy derivatives 1 – 4 (Figure 1).^{17, 18} All four compounds exhibited potent cytotoxicity against human pancreatic cancer cell lines (PANC-1, Mia PaCa-2 and BxPC-3) and induced caspase-dependent apoptosis. The mechanism of action was shown to involve quinone reduction, followed by loss of the phenoxide leaving group to generate an electrophilic iminium ion leading to irreversible inhibition of thioredoxin reductase (Scheme 1), and represents a potential novel molecular target in pancreatic cancer.¹⁷ Indolequinone 3 was subsequently studied in more detail and its effect on MAPK signalling pathways investigated.¹⁸ Inhibition of thioredoxin reductase leads to oxidation of thioredoxin, dissociation of free ASK1, phosphorylation of JNK and p38 and subsequent apoptosis.¹⁸

Scheme 1.

Reduction of indolequinones leading to loss of phenoxide and formation of an electrophilic iminium intermediate capable of inactivating an enzyme.

The incidence of pancreatic cancer is increasing and is the fourth leading cause of cancer deaths in Europe and the US. Currently the most viable treatment options are surgery and/or radiation with the value of chemotherapy being described as insignificant. Existing treatments are suboptimal, and the 5 year survival rate is amongst the most dismal of any tumour type at around 5%.¹⁹ Therefore novel therapeutic agents are urgently needed. In view of the biological activity of the indolequinones 1 – 4, we now report a study of a much wider range of 2-unsubstituted indolequinones 1 – 25 (Figure 2) with details of their synthesis, and structure activity relationships in terms of their cytotoxicity against Mia-PaCa human pancreatic tumour cells.

Figure 2.

Range of 2-unsubstituted indolequinones studied. R¹, R⁵, R⁶ and Y defined in Table 1.

Results and discussion

Chemistry

The key intermediates in the synthesis of indolequinones 1 – 25 are the corresponding 3-hydroxymethyl indolequinones 29. Previously, such indolequinones have been synthesized by us and others via the corresponding indole-3-carboxaldehyde or indole-3-carboxylate ester, with the quinone functionality introduced by the classical sequence of nitration, reduction and oxidation of the resulting aniline.^{20, 21} While these routes are effective, they are unsuited to the synthesis of large compound collections due to their laborious nature and poor functional group tolerance. In order to address this problem, we have recently developed a new route to indolequinones based on the regioselective reaction of bromoquinones with enamines.^{22, 23} Thus, reaction of bromo-5-methoxy-1,4-benzoquinone 26a with methyl 3-methylaminoacrylate 27a gave the indolequinone ester 28a in 40% yield (Scheme 2). Use of the isomeric 2-bromo-6-methoxy-1,4-benzoquinone 26b with the same enamine gave the corresponding 6-methoxyindolequinone 28b in 64% yield.

Scheme 2.

Synthesis of 3-hydroxymethylindolequinones [PMP = 4-methoxyphenyl, Morph = 4-morpholinyl].

The reduction of the ester functionality of the resulting indolequinones was found to be problematic; the best results were obtained by prior reduction of the quinone with sodium dithionite in a two phase system, followed by treatment with lithium aluminium hydride and subsequent re-oxidation of the hydroquinone with either air or iron(III) chloride. However, the yield for this sequence remained modest; the 3-hydroxymethyl indolequinones 29a and 29b were synthesized in 21% and 60% yield respectively. Most of the remaining material was either over-reduced to the corresponding 3-methylindolequinone or recovered as unreacted methyl ester.

Having developed a convergent route to the key 3-hydroxymethyl indolequinones 29, a range of compounds was synthesized, particular attention being paid to the substituent on the indole 1-position, where it was hoped that a water-solubilising functionality such as an alcohol or a tertiary amine could be incorporated. Whilst tertiary amines were tolerated by the synthetic route, the hydroxyethyl and hydroxypropyl groups had to be protected as their 4-methoxyphenyl ethers. To effect variation at the 1-position, the requisite enamines 27b – 27e were synthesized by conjugate addition of the corresponding primary amines to methyl propiolate. Additionally, in order to explore variation of the 5- and 6-positions, the bromoquinones 26c – 26e were subjected to our reaction conditions; these were either commercially available or could be easily synthesized from phenolic precursors.

With a range of 3-hydroxymethyl indolequinones 29 in hand, it only remained to convert the hydroxyl group into a better leaving group, since from previous work it is known that this is an essential requirement for biological activity (Scheme 1). Reaction of the 3-hydroxymethyl compounds 29 with thionyl chloride gave the corresponding chloromethyl derivative, which underwent reaction with the appropriate nucleophile in the presence of potassium carbonate to give the products 1 – 17 and 20 – 25. In cases where a PMP-protected alcohol was present, subsequent deprotection under oxidative conditions using cerium(IV) ammonium nitrate in aqueous DMF gave the corresponding alcohols 18 and 19.

Variations in the 1-position, the leaving group (Y, Scheme 2) and the 5- and 6-positions were studied in turn. Firstly, the leaving group was investigated; in addition to the previously studied 4-nitro- and 2,4,6-trifluoro-phenoxy derivatives 1 – 4, we prepared a range of indolequinones 5 – 9 bearing alternative phenolic leaving groups, including phenoxy itself, 4-methanesulfonylphenoxy, 4-carboxyphenoxy and 4-carboxy-2-fluorophenoxy. We next investigated alternatives to phenolic leaving groups and prepared a series of indolequinones 10 – 16 containing heterocyclic rings, chosen so that the leaving heterocycles has a pK_a value in the correct range (see below). All these examples were carried out in the 6-methoxyindolequinone series, with some replicated in the 5-methoxyindolequinone series, and the 1-substituent was maintained as a methyl group throughout.

Next, the indolequinones 17 – 21 were prepared in order to investigate the possibility of improving the water solubility via the incorporation of 2-hydroxyethyl, 3-hydroxypropyl, 2-dimethylaminoethyl, and 2-(4-morpholinyl)ethyl groups in the 1-position. Again, these compounds exclusively bear a 6-methoxy group, and used the 2,4,6-trifluorophenoxy leaving group. Finally, some minor variations at the 5- and 6-positions were studied with compounds 22– 25.

Biology

The indolequinones were assayed for their effect on the growth of human pancreatic cancer cells using the MTT assay in the Mia Paca-2 cell line. Cell growth was measured after 4 and 72 hour treatment using previously described methods,¹⁷ and the results are shown in Table 1. For comparison data for gemcitabine, one of the current standard chemotherapeutic treatments for pancreatic cancer are also presented. The data, which include the previously described compounds 1 – 4 for completeness, enable a number of conclusions about the structural requirements for cytotoxicity to be made. Firstly, as previously established for indolequinones 1 – 4, the location of the methoxy group at C-5 or C-6 makes little difference to the cytotoxicity towards Mia Paca-2 cells (Entries 1 vs. 2, 3 vs. 4, 6 vs. 7), although the pair of N-hydroxysuccinimide derivatives (Entries 11 and 12) appear to be an exception. Secondly in terms of the substituent Y, the ability of the group to act as a leaving group upon reductive activation of the quinone is clearly an important factor. 4-Nitrophenol and 2,4,6-trifluorophenol have similar pK_a values (7.2 and 7.5 respectively) and in the 5- and 6-methoxy indolequinones, compounds containing these leaving groups are generally among the most cytotoxic (Entries 1–4, 18–23). A poorer leaving such as phenol itself (pK_a 9.9) results in a less cytotoxic compound (Entry 5) whereas use of a 4-methanesulfonylphenol leaving group (pK_a 7.5) restores biological activity (Entries 6 and 7). The indolequinones 8 and 9, incorporating phenolic substituents (pK_a 8.3 and 7.1 respectively) designed to increase solubility, are somewhat less active. As alternatives to phenolic leaving groups, the indolequinones 10 – 16 containing heterocyclic rings were next studied. Incorporation of succinimide (pK_a 9.6), 1,2,3-triazole (pK_a 8.7), and tetrazole (pK_a 4.7) as potential leaving groups resulted in non-toxic compounds (Entries 10, 13–16), whereas use of N-hydroxysuccinimide (pK_a 7.8) in the 6-methoxyindolequinone series (Entry 12) resulted in a highly cytotoxic compound. Hence, although the pK_a of the leaving group is clearly an important factor, there is not a simple linear relationship between pK_a and potency of the indolequinone.

Table 1.

Cytotoxicity of 2-unsubstituted indolequinones towards Mia PaCa-2 tumour cells after 4 and 72 hours exposure.

Entry	Cpd	R1 a	Y b	R5	R6	IC50 c 4 h /nM	IC50 c 72 h /nM
1	1	Me	O(4-NO2C6H4)	OMe	H	39±13	24±6
2	2	Me	O(4-NO2C6H4)	H	OMe	32±9	18±5
3	3	Me	OAr	OMe	H	34±9	18±6
4	4	Me	OAr	H	OMe	26±7	19±4
5	5	Me	OPh	H	OMe	276±26	122±18
6	6	Me	O(4-MeSO2C6H4)	OMe	H	31±6	24±4
7	7	Me	O(4-MeSO2C6H4)	H	OMe	29±8	31±6
8	8	Me	O(4-HO2CC6H4)	H	OMe	110±15	50±10
9	9	Me	O(2-F-4-HO2CC6H4)	H	OMe	198±16	56±5
10	10	Me	N-Succinimidyl	H	OMe	NT	NT
11	11	Me	O-N-Succinimidyl	OMe	H	178±30	127±18
12	12	Me	O-N-Succinimidyl	H	OMe	42±13	26±4
13	13	Me	1,2,3-triazol-1-yl	H	OMe	NT	NT
14	14	Me	1,2,3-triazol-2-yl	H	OMe	NT	NT
15	15	Me	1-tetrazolyl	H	OMe	NT	NT
16	16	Me	2-tetrazolyl	H	OMe	NT	NT
17	17	(CH2)2OPMP	OAr	H	OMe	68±8	27±3
18	18	(CH2)2OH	OAr	H	OMe	64±9	34±5
19	19	(CH2)3OH	OAr	H	OMe	64±9	34±7
20	20	(CH2)2NMe2	OAr	H	OMe	51±9	35±7
21	21	(CH2)2Morpholinyl	OAr	H	OMe	35±3	17±2
22	22	(CH2)2Morpholinyl	OAr	H	OEt	242±36	137±22
23	23	(CH2)2Morpholinyl	OAr	OMe	Me	120±32	65±15
24	24	Me	O-N-Succinimidyl	benzo		NT	NT
25	25	Me	O(4-MeSO2C6H4)	benzo		NT	NT
26	gemcitabine		-	-		359±45	25±4

Notes

Compounds 1 – 4 also described in reference 17.

^aPMP = 4-methoxyphenyl, Morph = 4-morpholinyl

^bAr = 2,4,6-trifluorophenyl unless otherwise stated

^cNT = non toxic (IC₅₀ > 5 μM)

The substituent on the indolequinone nitrogen appears to have little effect on biological activity, and a range of groups containing substituents likely to increase aqueous solubility are well tolerated. Thus the indolequinones containing N-hydroxyalkyl or -aminoalkyl groups 18 – 21 are all highly cytotoxic. Less well tolerated are changes to the indolequinone 5- and 6-positions. Replacement of methoxy by ethoxy or inclusion of an additional methyl group results in lower toxicity (Entries 22 and 23), while fusion of an additional benzene ring results in non-toxic quinones (Entries 24 and 25).

The more potent compounds (Table 1, Entries 1–4, 6, 7, 21) are all more potent than gemcitabine at the 4 hour treatment point, and equipotent at the 72 hour point suggesting this series of indolequinones is worthy of further investigation. Therefore two of the more potent compounds, 2 and 3, were tested against a small range of other tumour cell lines (Table 2).

Table 2.

Cytotoxicity of indolequinones 2 and 3 towards tumour cells after 4 and 72 hours exposure.

Entry	Cell line	Compound 2 IC50 (nM)		Compound 3 IC50 (nM)
		4 h	72 h	4 h	72 h
1	Panc1	49 ± 4	24 ± 3
2	BxPC-3	126 ± 14	58 ± 8	100 ± 11	43 ± 10
3	Jurkat	328 ± 14
4	KG1A	804 ± 6
5	MDA468	244 ± 26
6	SKMEL-5			96 ± 4	46 ± 5

High potency was retained against other human pancreatic cell lines (Entries 1 and 2), and also observed, for compound 3, against a melanoma line (Entry 6). On the other hand, compound 2 was less potent against leukaemia and breast lines (Entries 3–5). These data are similar to previously published results obtained with indolequinones in the National Cancer Institute’s 60-cell line screen which showed that breast cancer and leukaemia cell lines to be relatively resistant to these agents.¹⁷

Conclusions

The reaction of bromoquinones with enamines provides a convenient route to indolequinone-3-carboxylates, converted into novel indolequinones containing a range of substituents on the indolic nitrogen and leaving groups at the 3-indolylmethyl position. Subsequently they were tested for their ability to inhibit the growth of human pancreatic cancer cells. A number of potent inhibitors have been identified, and the key structural features for biological activity delineated. More detailed biological evaluation of key compounds is in progress.

Experimental section

General experimental details

Commercially available reagents were used throughout without purification unless otherwise stated. All anhydrous solvents were used as supplied, except tetrahydrofuran and dichloromethane that were freshly distilled according to standard procedures. Reactions were routinely carried out under an argon atmosphere unless otherwise stated, and all glassware was flame-dried before use. Light petroleum refers to the fraction with bp 40–60 °C. Ether refers to diethyl ether.

Analytical thin layer chromatography was carried out on aluminium backed plates coated with silica gel, and visualized under UV light at 254 and/or 360 nm and/or by chemical staining. Flash chromatography was carried out using silica gel, with the eluent specified.

Infrared spectra were recorded using an FT-IR spectrometer over the range 4000-600 cm⁻¹. NMR spectra were recorded at 400 or 500 MHz (¹H frequency, 100 or 125 MHz ¹³C frequency). Chemical shifts are quoted in parts per million (ppm), and are referenced to residual H in the deuterated solvent as the internal standard. Coupling constants, J, are quoted in Hz. In the ¹³C NMR spectra, signals corresponding to CH, CH₂, or CH₃ groups are assigned from the DEPT spectra all others are C. Mass spectra were recorded on a time-of-flight mass spectrometer using electrospray ionization (ESI), or an EI magnetic sector instrument.

General Procedure 1: Copper(II) acetate mediated synthesis of indolequinone-3-esters

A solution of enamine (1.0–4.0 mol equiv) in acetonitrile (5–10 mL/mmol) was added to a mixture of bromoquinone (1.0 mol equiv), copper(II) acetate monohydrate (2.0 mol equiv) and potassium carbonate (3.0 mol equiv). The resulting mixture was stirred at reflux for the indicated time, cooled to room temperature and diluted with dichloromethane (20 mL/mmol), filtered through Celite and concentrated in vacuo. Column chromatography of the residue gave the indolequinone.

General Procedure 2: Synthesis of indolequinone-3-carbinols

A solution of sodium dithionite (5 mol equiv) in water (10 mL / mmol) was added to a solution of the indolequinone-3-ester in chloroform (10 mL / mmol), and the resulting mixture was stirred at room temperature under argon for 2 h, then extracted with dichloromethane. The combined organic phases were dried (MgSO₄), filtered and concentrated, and dried under vacuum for ~1 h. The residue was dissolved in THF (10–20 mL / mmol), and lithium aluminium hydride (5 mol equiv) was added portionwise. The resulting mixture was stirred at room temperature for 2 h and quenched by sequential slow addition of ethyl acetate (~5 mL / mmol), water (~1 mL / mmol), aqueous sodium hydroxide solution (1 M; ~1 mL / mmol) and silica gel (~100 mg / mmol). The quenched mixture was stirred under air for 30 min, filtered and concentrated. Column chromatography gave the alcohol product.

In cases where the aerobic oxidation of the hydroquinone was slow, the quenched mixture was immediately filtered and concentrated, and dissolved in methanol (10 mL / mmol). A solution of iron(III) chloride hexahydrate (5 mol equiv) in water (10 mL / mmol) was added, and the mixture was stirred at room temperature for 1 h, concentrated to half its volume and extracted with dichloromethane. The combined extracts were dried (MgSO₄), filtered and concentrated. Column chromatography of the residue gave the product.

General Procedure 3: Synthesis of 3-indolequinonylmethyl ethers

Thionyl chloride (10 mol equiv) was added to a stirred solution of the alcohol in dichloromethane (10 mL / mmol), and the resulting mixture was stirred at room temperature for 3–7 h, concentrated and azeotroped with two further portions of dichloromethane. The residue was dissolved in DMF (10 mL / mmol) and the appropriate nucleophile (5 mol equiv) was added. When this had dissolved, potassium carbonate (5 mol equiv) was added, and the mixture was stirred for 14–18 h, diluted with water and extracted with ethyl acetate. The combined extracts were washed with water, dried (MgSO₄), filtered and concentrated. Column chromatography of the residue gave the product.

2-Bromo-5-methoxy-1,4-benzoquinone 26a

Prepared as previously described.²³

2-Bromo-6-methoxy-1,4-benzoquinone 26b

Prepared as previously described.²³

2,4-Dibromo-6-ethoxyphenol

A solution of bromine (6.56 g, 41 mmol) in dichloromethane (20 mL) was added over 40 min to a stirred solution of 2-ethoxyphenol (2.76 g, 20 mmol) in dichloromethane (80 mL) at 0 °C. The mixture was stirred at room temperature for 2 h, washed with saturated aqueous sodium thiosulfate solution (2 × 50 mL), dried (MgSO₄), filtered and concentrated to give the title compound as a colourless solid (5.74 g, 97%), mp 89–91 °C; ν_max (CHCl₃)/cm⁻¹ 3538, 2987, 1494, 1565; δ_H (400 MHz; CDCl₃) 7.20 (1H, s, ArH), 7.07 (1H, s, ArH), 5.65 (1H, br s, OH), 4.11 (2H, q, J 7.0, CH₂), 1.48 (3H, t, J 7.0, Me); δ_C (75 MHz; CDCl₃) 145.7, 124.0, 119.1 (CH), 116.1 (CH), 115.3, 113.7, 65.1 (CH₂), 14.7 (Me).

2-Bromo-6-ethoxy-1,4-benzoquinone 26c

A solution of chromium(VI) oxide (2.107 g, 21.1 mmol) in water (10 mL) was added to a stirred solution of 2,4-dibromo-6-ethoxyphenol (5.67 g, 19.2 mmol) in acetic acid (20 mL), acetonitrile (10 mL) and water (5 mL), and the resulting mixture was stirred at 60 °C for 1.5 h, cooled to room temperature, diluted with water (150 mL) and extracted with chloroform (4 × 50 mL). The combined organic phases were dried (MgSO₄), filtered and concentrated. Column chromatography eluting with dichloromethane and light petroleum (1:1 then 2:1) gave the title compound as an orange solid (2.07 g, 47%), mp 82–84 °C; (Found: M+Na⁺, 252.9487. C₈H₇⁷⁹BrO₃Na requires 252.9471); ν_max (CHCl₃)/cm⁻¹ 2992, 1680, 1656, 1586, 1182; δ_H (400 MHz; CDCl₃) 7.20 (1H, s, CH), 5.95 (1H, s, CH), 4.05 (2H, q, J 7.0, CH₂), 1.51 (3H, t, J 7.0, Me); δ_C (75 MHz; CDCl₃) 184.9, 174.6, 157.5, 138.4 (CH), 134.3, 107.9 (CH), 65.9 (CH₂), 13.8 (Me); m/z (ESI) 253 (M+Na⁺, 88%), 413 (100).

4,6-Dibromo-3-methoxy-2-methylphenol

A solution of bromine (2.797 g, 17.48 mmol) in dichloromethane (8 mL) was added over 15 min to a stirred solution of 2-methyl-3-methoxyphenol (1.206 g, 8.74 mmol) in dichloromethane (13 mL). The mixture was stirred at room temperature for 1.5 h, washed with saturated sodium thiosulfate solution (50 mL) and brine (50 mL), dried (MgSO₄), filtered and concentrated to give the title compound as a colourless solid (2.417 g, 93%), mp 64–66 °C; (Found: M−H⁻, 292.8821. C₈H₇O₂⁷⁹Br₂Na requires 292.8818); ν_max (CHCl₃)/cm⁻¹ 3519, 3007, 2940, 1601, 1459, 1439; δ_H (400 MHz; CDCl₃) 7.54 (1H, s, CH), 5.56 (1H, br s, OH), 3.81 (3H, s, Me), 2.30 (3H, s, Me); δ_C (75 MHz; CDCl₃) 155.8, 150.8, 131.3 (CH), 121.0, 107.9, 105.3, 60.5 (Me), 10.6 (Me); m/z (ESI) 293/295/297 (M−H⁻, 52/100/60%).

5-Bromo-2-methoxy-3-methyl-1,4-benzoquinone 26d

A solution of chromium(VI) oxide (0.892 g, 8.92 mmol) in water (4 mL) was added to a stirred solution of 4,6-dibromo-3-methoxy-2-methylphenol (2.40 g, 8.11 mmol) in acetic acid (12 mL), acetonitrile (12 mL) and water (8 mL), and the resulting mixture was stirred at 60 °C for 2 h. After cooling to room temperature, the mixture was diluted with water (100 mL) and extracted with dichloromethane (3×50 mL). The combined organic phases were dried (MgSO₄), filtered and concentrated. Column chromatography eluting with dichloromethane and light petroleum (1:1) gave the title compound as an orange solid (1.12 g, 60%), mp 52–54 °C; (Found: M+Na⁺, 252.9443. C₈H₇O₃⁷⁹BrNa requires 252.9476); ν_max (CHCl₃)/cm⁻¹ 2951, 1667, 1590, 1323; δ_H (400 MHz; CDCl₃) 7.14 (1H, s CH), 4.08 (3H, s, Me), 2.05 (3H, s, Me); δ_C (75 MHz; CDCl₃) 180.9, 180.3, 155.6, 137.6, 135.9 (CH), 128.5, 61.1 (Me), 9.8 (Me); m/z (ESI) 253/255 (M+Na⁺, 33/34%), 413 (100).

Methyl 3-(methylamino)acrylate 27a

Prepared as previously described.²³

tert-Butyl (2-bromoethyl)carbamate²⁴

Triethylamine (20 mL) was added as a single portion to a stirred suspension of 2-bromoethylamine hydrobromide (8.20 g, 40 mmol) and di-tert-butyl dicarbonate (8.72 g, 40 mmol) in dichloromethane (200 mL), and the mixture was stirred at room temperature for 15 h, washed with water (100 mL), dried (MgSO₄), filtered and concentrated. Column chromatography eluting with ether and light petroleum (1:4) gave the title compound as a colourless oil (6.92 g, 77%); δ_H (400 MHz; CDCl₃) 5.00 (1H, br s, NH), 3.55 (2H, dt, J 5.6, 5.4, CH₂N), 3.47 (2H, t, J 5.6, CH₂), 1.47 (9H, s, tBu); δ_C (75 MHz; CDCl₃) 156.2, 79.9, 42.4 (CH₂), 32.9 (CH₂), 28.4 (Me). NMR data matches literature values.²⁴

2-(4-Methoxyphenoxy)ethylamine

Potassium carbonate (8.223 g, 59.6 mmol) was added to a stirred solution of tert-butyl (2-bromoethyl)carbamate (4.449 g, 19.9 mmol) and 4-methoxyphenol (7.389 g, 59.6 mmol) in DMF (50 mL), and the resulting mixture was stirred at 50 °C for 15 h. Water (350 mL) was added, and the mixture was extracted with ethyl acetate (3 × 100 mL). The combined organic phases were dried (MgSO₄), filtered and concentrated. Column chromatography eluting with ethyl acetate and light petroleum (1:7) gave an inseparable mixture of 4-methoxyphenol and the 4-methoxyphenyl ether. This mixture was dissolved in dichloromethane (100 mL) and trifluoroacetic acid (20 mL) was added. The mixture was stirred at room temperature for 4 h and extracted with water (3 × 150 mL). The combined aqueous phases were basified to pH 14 with sodium hydroxide pellets at 0 °C and extracted with dichloromethane (3 × 100 mL). The combined organic extracts were dried (Na₂SO₄), filtered and concentrated to give the title compound as a colourless solid (2.200 g, 81%), mp 37–39 °C; (Found: M+H⁺, 168.1033. C₉H₁₄NO₂ requires 168.1019); ν_max (CHCl₃)/cm⁻¹ 3443, 3011, 2653, 1686, 1602, 1509; δ_H (400 MHz; CDCl₃) 6.87 (2H, d, J 9.2, ArH), 6.84 (2H, d, J 9.2, ArH), 3.95 (2H, t, J 5.2, CH₂), 3.78 (3H, s, Me), 3.07 (2H, t, J 5.2, CH₂), 1.44 (2H, br s, NH₂); δ_C (75 MHz; CDCl₃) 153.9, 153.1, 115.5 (CH), 114.7 (CH), 70.9 (CH₂), 55.7 (Me), 41.7 (CH₂); m/z (ESI) 168 (M+H⁺, 9%), 218 (100).

Methyl 3-[2-(4-methoxyphenoxy)ethylamino]acrylate 27b

2-(4-Methoxyphenoxy)ethylamine (2.200 g, 13.2 mmol) was added over 5 min to a stirred solution of methyl propiolate (1.107 g, 13.2 mmol) in dichloromethane (26 mL), and the mixture was stirred at room temperature for 20 h and concentrated to give the title compound as an off-white solid (3.19 g, 96%), 2:1 cis:trans; mp 85–87 °C; (Found: M+Na⁺, 274.1022. C₁₃H₁₇NO₄Na requires 274.1050); ν_max (CHCl₃)/cm⁻¹ 3447, 3010, 2951, 1685, 1621, 1508; δ_H (400 MHz; CDCl₃) major isomer: 8.03 (1H, br s, NH), 6.86 (4H, s, ArH), 6.73 (1H, dd, J 13.2, 8.0, CH), 4.55 (1H, d, J 8.0, CH), 4.00 (2H, t, J 5.5, CH₂O), 3.79 (3H, s, Me), 3.67 (3H, s, Me), 3.54 (2H, q, J 5.5, CH₂); minor isomer: 7.58 (1H, dd, J 13.0, 8.2, CH), 6.86 (4H, s, ArH), 4.88 (1H, br s, NH), 4.83 (1H, d, J 13.0, CH), 4.08 (2H, t, J 5.2, CH₂), 3.79 (3H, s, Me), 3.70 (3H, s, Me), 3.44 (2H, q, J 5.2, CH₂); δ_C (75 MHz; CDCl₃) mixture: 171.1, 169.8, 154.3, 154.2, 152.6, 152.4 (CH), 152.3, 149.1 (CH), 116.0 (CH), 115.6 (CH), 114.8 (CH), 114.6 (CH), 86.3 (CH), 82.4 (CH), 68.7 (CH₂), 66.4 (CH₂), 55.7 (Me), 50.6 (Me), 50.2 (Me), 47.9 (Me); m/z (ESI) 274 (M+Na⁺, 100%).

tert-Butyl (3-bromopropyl)carbamate²⁵

Triethylamine (15 mL) was added over 1 min to a stirred suspension of 3-bromopropylamine hydrobromide (6.57 g, 30 mmol) and di-tert-butyl dicarbonate (6.54 g, 30 mmol) in dichloromethane (150 mL). The mixture was stirred at room temperature for 17 h, washed with water (100 mL), dried (MgSO₄), filtered and concentrated. Column chromatography eluting with ether and light petroleum (1:4) gave the title compound as a colourless oil (6.205 g, 87%); ν_max (CHCl₃)/cm⁻¹ 3449, 3251, 1703, 1490; δ_H (400 MHz; CDCl₃) 4.72 (1H, br s, NH), 3.45 (2H, t, J 6.5, CH₂), 3.28 (q, J 6.5, CH₂), 2.06 (2H, pent, J 6.5, CH₂), 1.45 (9H, s, tBu); δ_C (75 MHz; CDCl₃) 156.0, 79.4, 32.7 (CH₂), 30.8 (CH₂), 28.4 (Me), 27.4 (CH₂).

3-(4-Methoxyphenoxy)propyl-1-amine

Potassium carbonate (6.21 g, 45 mmol) was added to a stirred solution of tert-butyl (3-bromopropyl)carbamate (3.57 g, 15 mmol) and 4-methoxyphenol (5.58 g, 45 mmol) in DMF (60 mL) at room temperature. The resulting mixture was stirred at 50 °C for 17 h, diluted with water (350 mL) and extracted with ethyl acetate (4 × 75 mL). The combined organic phases were washed with water (100 mL), dried (MgSO₄), filtered and concentrated. Column chromatography eluting with ether and light petroleum (1:3) gave an inseparable mixture of 4-methoxyphenol and the intermediate.

This mixture was dissolved in dichloromethane (75 mL), and trifluoroacetic acid (15 mL) was added as a single portion. The resulting mixture was stirred at room temperature for 3 h and extracted with water (3 × 50 mL). The combined aqueous extracts were basified to pH 14 with sodium hydroxide pellets at 0 °C and extracted with dichloromethane (4 × 50 mL). The combined organic extracts were dried (Na₂SO₄), filtered and concentrated to give the title compound as an off-white solid (2.359 g, 87%), mp 42–44 °C; (Found: M+Na⁺, 182.1175. C₁₀H₁₆NO₂Na requires 182.1176); ν_max (CHCl₃)/cm⁻¹ 3010, 2952, 1591, 1509, 1468; δ_H (400 MHz; CDCl₃) 6.85 (4H, s, ArH), 4.05 (2H, t, J 6.2, CH₂), 3.78 (3H, s, Me), 2.92 (2H, t, J 6.8, CH₂), 1.92 (2H, tt, J 6.8, 6.2, CH₂); δ_C (75 MHz; CDCl₃) 153.8, 153.1, 115.4 (CH), 114.6 (CH), 66.5 (CH₂), 55.7 (Me), 39.3 (CH₂), 33.2 (CH₂); m/z (ESI) 182 (M+H⁺, 100%).

Methyl 3-[3-(4-methoxyphenoxy)propylamino]acrylate 27c

Methyl propiolate (1.510 g, 18 mmol) was added over 3 min to a stirred solution of 3-(4-methoxyphenoxy)propyl-1-amine (3.254 g, 18 mmol) in acetonitrile (20 mL) at room temperature. The resulting mixture was stirred at room temperature for 14 h and concentrated to give the title compound as a pale yellow oil (4.721 g, 99%), 1.5:1 cis:trans, (Found: M+Na⁺, 288.1186. C₁₄H₁₉NO₄Na requires 288.1212); ν_max (CHCl₃)/cm⁻¹ 3446, 3010, 2953, 1719, 1665, 1617, 1509, 1441; δ_H (400 MHz; CDCl₃) major isomer: 7.91 (1H, br s, NH), 6.87-6.84 (4H, m, ArH), 6.65 (1H, dd, J 13.1, 8.0, CH), 4.49 (1H, d, J 8.0, CH), 4.03-3.98 (2H, m, CH₂), 3.80 (3H, s, Me), 3.67 (3H, s, Me), 3.42 (2H, dt, J 6.5, 6.4, CH₂), 2.00 (2H, tt, J 6.4, 6.0, CH₂); minor isomer: 7.54 (1H, dd, J 13.3, 8.2, CH), 6.87-6.84 (4H, m, ArH), 4.86 (1H, br s, NH), 4.79 (1H, d, J 13.3, CH), 4.03-3.98 (2H, m, CH₂), 3.80 (3H, s, Me), 3.69 (3H, s, Me), 3.30 (2H, dt, J 6.4, 6.0, CH₂), 2.05 (2H, tt, J 6.4, 6.1, CH₂); δ_C (75 MHz; CDCl₃) mixture: 171.2, 170.0, 154.1, 154.0, 152.8, 152.6, 152.5 (CH), 116.0 (CH), 115.5 (CH), 115.4 (CH), 114.8 (CH), 114.7 (CH), 114.6 9 (CH), 81.6 (CH), 66.6 (CH₂), 65.2 (CH₂), 55.7 (Me), 50.6 (Me), 50.2 (Me), 45.5 (CH₂), 31.0 (CH₂); m/z (ESI) 288 (M+Na⁺, 49%), 302 (100).

Methyl 3-(2-dimethylaminoethylamino)acrylate 27d

N,N-Dimethylethylenediamine (1.76 g, 20 mmol) was added over 5 min to a stirred solution of methyl propiolate (1.68 g, 20 mmol) in acetonitrile (10 mL), and the resulting mixture was stirred at room temperature for 14 h and concentrated to give the title compound as a pale yellow oil (3.42 g, 99%), 1:2.5 cis:trans, (Found: M+H⁺, 173.1296. C₈H₁₇N₂O₂ requires 173.1285); ν_max (CHCl₃)/cm⁻¹ 3401, 3011, 2951, 1665, 1615, 1438; δ_H (400 MHz; CDCl₃) major isomer: 7.57 (1H, dd, J 13.2, 7.8, CH), 5.19 (1H, br s, NH), 4.71 (1H, d, J 13.2, CH), 3.68 (3H, s, Me), 3.08 (2H, dt, J 6.1, 5.3, CH₂), 2.51 (2H, t, J 6.1, CH₂), 2.25 (6H, s, Me); minor isomer: 7.90 (1H, br s, NH), 6.66 (1H, dd, J 13.3, 8.1, CH), 4.50 (1H, d, J 8.1, CH), 3.66 (3H, s, Me), 3.27 (2H, dt, J 6.5, 6.2, CH₂), 2.46 (2H, J 6.5, CH₂), 2.28 (6H, s, Me); δ_C (75 MHz; CDCl₃) mixture: 171.0, 170.0, 152.1 (CH), 149.0 (CH), 85.3 (CH), 81.7 (CH), 59.9 (CH₂), 57.7 (CH₂), 50.5 (Me), 50.2 (Me), 48.0 (CH₂), 46.5 (CH₂), 45.6 (Me), 44.9 (Me); m/z (ESI) 173 (M+H⁺, 59%), 225 (90), 257 (100).

Methyl 3-[(2-morpholinoethyl)amino]acrylate 27e

1-(2-Aminoethyl)morpholine (2.60 g, 20 mmol) was added over 5 min to a stirred solution of methyl propiolate (1.68 g, 20 mmol) in acetonitrile (10 mL), and the resulting mixture was stirred at room temperature for 15 h and concentrated to give the title compound as a pale yellow oil (4.28 g, 100%), 1:2 cis:trans; (Found: M+H⁺, 215.1388. C₁₀H₁₉N₂O₃ requires 215.1396); ν_max (CHCl₃)/cm⁻¹ 3412, 3011, 2949, 2820, 1671, 1618; δ_H (400 MHz; CDCl₃) major isomer: 6.66 (1H, dd, J 13.2, 8.0, CH), 5.12 (1H, br s, NH), 4.50 (1H, d, J 8.0, CH), 3.75-3.71 (4H, m, CH₂), 3.67 (3H, s, Me), 3.30 (2H, dt, J 6.3, 6.2, CH₂), 2.53 (2H, t, J 6.3, CH₂), 2.50-2.45 (4H, m, CH₂); minor isomer: 7.90 (1H, br s, NH), 7.58 (1H, dd, J 7.8, 13.3, CH), 4.73 (1H, d, J 13.3, CH), 3.75-3.71 (4H, m, CH₂O), 3.69 (3H, s, Me), 3.10 (2H, dt, J 5.9, 5.4, CH₂), 2.59 (2H, t, J 5.9, CH₂), 2.50-2.45 (4H, m, CH₂); δ_C (75 MHz; CDCl₃) mixture: 171.0, 169.9, 152.0 (CH), 148.9 (CH), 85.6 (CH), 81.8 (CH), 67.0 (CH₂), 59.1 (CH₂), 56.0 (CH₂), 53.7 (CH₂), 53.1 (CH₂), 50.6 (Me), 50.2 (Me), 45.5 (CH₂); m/z (ESI) 215 (M+H⁺, 100%), 237 (M+Na⁺, 67), 451 (2M+Na⁺, 64).

Methyl 5-methoxy-1-methyl-4,7-dioxo-1H-indole-3-carboxylate 28a

Prepared by general procedure 1 from methyl 3-(methylamino)acrylate 27a (4.24 g, 36.9 mmol), 2-bromo-5-methoxy-1,4-benzoquinone 26a (4.00 g, 18.4 mmol), copper(II) acetate monohydrate (5.52 g, 27.7 mmol) and potassium carbonate (7.64 g, 55.3 mmol), stirred at reflux in acetonitrile (180 mL). Column chromatography eluting with ethyl acetate and dichloromethane (1:19) gave the title compound as a yellow-orange solid (1.83 g, 40%); mp 212–214 °C; (Found: M+Na⁺, 272.0521. C₁₂H₁₁NO₅Na requires 272.0529); ν_max (CHCl₃)/cm⁻¹ 3011, 1733, 1688, 1650, 1606, 1268, 1239, 1027; δ_H (400 MHz; CDCl₃) 7.39 (1H, s, CH), 5.72 (1H, s, CH), 4.00 (3H, s, Me), 3.88 (3H, s, Me), 3.84 (3H, s, CO₂Me); δ_C (100 MHz; CDCl₃) 179.3, 175.0, 162.8, 160.9, 134.6 (CH), 131.2, 121.9, 114.7, 105.8 (CH), 56.7 (Me), 51.9 (Me), 37.0 (Me).

Methyl 6-methoxy-1-methyl-4,7-dioxo-1H-indole-3-carboxylate 28b

Prepared as previously described.²³

Methyl 6-methoxy-1-[2-(4-methoxyphenoxy)ethyl]-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28c

Prepared by general procedure 1 from methyl 3-([2-(4-methoxyphenoxy)ethyl]amino)acrylate 27b (2.51 g, 10 mmol), 2-bromo-6-methoxy-1,4-benzoquinone 26b (2.17 g, 10 mmol), copper(II) acetate monohydrate (3.99 g, 20 mmol) and potassium carbonate (4.14 g, 30 mmol) stirred at reflux in acetonitrile (100 mL) for 15 h. Column chromatography eluting with ethyl acetate and dichloromethane (1:9) gave the title compound as a yellow solid (1.607 g, 42%), mp 123–125 °C; (Found: M+Na⁺, 408.1054. C₂₀H₁₉NO₇Na requires 408.1054); ν_max (CHCl₃)/cm⁻¹ 3008, 2954, 1737, 1677, 1602, 1538, 1509; δ_H (400 MHz; CDCl₃) 7.67 (1H, s, CH), 6.83 (2H, d, J 9.3, ArH), 6.78 (2H, d, J 9.3, ArH), 5.84 (1H, s, CH), 4.76 (2H, t, J 4.8, CH₂), 4.27 (2H, t, J 4.8, CH₂), 3.92 (3H, s, Me), 3.85 (3H, s, Me), 3.78 (3H, s, Me); δ_C (75 MHz; CDCl₃) 180.8, 173.2, 162.7, 158.3, 154.4, 152.0, 136.6 (CH), 128.7, 125.5, 115.6 (CH), 114.8 (CH), 114.6, 108.6 (CH), 67.0 (CH₂), 56.7 (Me), 55.7 (Me), 52.0 (Me), 49.5 (CH₂); m/z (ESI) 408 (M+Na⁺, 76%), 793 (2M+Na⁺, 100).

Methyl 6-methoxy-1-[3-(4-methoxyphenoxy)propyl]-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28d

Prepared by general procedure 1 from methyl 3-([3-(4-methoxyphenoxy)propyl]amino)acrylate 27c (1.060 g, 4.0 mmol), 2-bromo-6-methoxy-1,4-benzoquinone 26b (0.868 g, 4.0 mmol), copper(II) acetate monohydrate (1.596 g, 8.0 mmol) and potassium carbonate (1.656 g, 12.0 mmol) stirred at reflux in acetonitrile (40 mL) for 14 h. Column chromatography eluting with ethyl acetate and dichloromethane (1:11) gave the title compound as a yellow solid (0.899 g, 56%), mp 80–82 °C; (Found: M+Na⁺, 422.1219. C₂₁H₂₁NO₇Na requires 422.1210); ν_max (CHCl₃)/cm⁻¹ 3011, 1734, 1671, 1656, 1610, 1509; δ_H (400 MHz; CDCl₃) 7.50 (1H, s, CH), 6.83-6.82 (4H, m, ArH), 5.82 (1H, s, CH), 4.58 (2H, t, J 6.7, CH₂), 3.92 (2H, t, J 5.7, CH₂), 3.86 (3H, s, Me), 3.83 (3H, s, Me), 3.78 (3H, s, Me), 2.27 (2H, tt, J 6.7, 5.7, CH₂); δ_C (75 MHz; CDCl₃) 180.9, 172.8, 162.6, 158.4, 154.1, 152.4, 165.6 (CH), 129.0, 125.4, 115.4 (CH), 114.7 (CH), 114.5, 108.5 (CH), 64.8 (CH₂), 56.6 (Me), 55.7 (Me), 51.9 (Me), 47.2 (CH₂), 30.0 (CH₂); m/z (ESI) 422 (M+Na⁺, 100%).

Methyl 1-[2-(dimethylamino)ethyl]-6-methoxy-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28e

Prepared by general procedure 1 from methyl 3-([2-(dimethylamino)ethyl]amino)acrylate 27d (0.516 g, 3.0 mmol), 2-bromo-6-methoxy-1,4-benzoquinone 26b (0.651 g, 3.0 mmol), copper(II) acetate monohydrate (1.197 g, 6.0 mmol) and potassium carbonate (1.242 g, 9 mmol) stirred at reflux in acetonitrile (30 mL) for 15 h. Column chromatography eluting with methanol, ethyl acetate and triethylamine (1:19:0.1) gave the title compound as a red solid (0.688 g, 75%), mp 108–110 °C; (Found: M+H⁺, 323.1227. C₁₅H₁₈N₂O₇ requires 323.1238); ν_max (CHCl₃)/cm⁻¹ 3008, 2952, 1733, 1670, 1655, 1610, 1536, 1243; δ_H (400 MHz; CDCl₃) 7.56 (1H, s, CH), 5.83 (1H, s, CH), 4.47 (2H, t, J 6.5, CH₂), 3.90 (3H, s, Me), 3.85 (3H, s, Me), 2.69 (2H, t, J 6.5, CH₂), 2.31 (6H, s, Me); δ_C (75 MHz; CDCl₃) 181.0, 172.9, 162.7, 158.3, 135.7 (CH), 129.0, 125.2, 114.6, 108.5 (CH), 59.1 (CH₂), 56.6 (Me), 52.0 (Me), 47.6 (CH₂), 45.5 (Me); m/z (ESI) 323 (M+Na⁺, 33%), 307 (100).

Methyl 6-methoxy-1-(2-morpholinoethyl)-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28f

Prepared by general procedure 1 from methyl 3-[(2-morpholinoethyl)amino]acrylate 27e (0.856 g, 4.0 mmol), 2-bromo-6-methoxy-1,4-benzoquinone 26b (0.868 g, 4.0 mmol), copper(II) acetate monohydrate (1.596 g, 8.0 mmol) and potassium carbonate (1.656 g, 12 mmol) stirred at reflux in acetonitrile (40 mL) for 4 h. Column chromatography eluting with methanol and ethyl acetate (1:9) gave the title compound as an orange-brown solid (0.976 g, 80%), mp 156–158 °C; (Found: M+Na⁺, 371.1203. C₁₇H₂₀N₂O₅Na requires 371.1214); ν_max (CHCl₃)/cm⁻¹ 3011, 2953, 1734, 1670, 1656, 1610, 1536; δ_H (400 MHz; CDCl₃) 7.55 (1H, s, CH), 5.85 (1H, s, CH), 4.50 (2H, t, J 6.5, CH₂), 3.92 (3H, s, Me), 3.86 (3H, s, Me), 3.69 (4H, t, J 4.6, CH₂O), 2.75 (2H, t, J 6.5, CH₂), 2.53 (4H, t, J 4.6, CH₂); δ_C (75 MHz; CDCl₃) 181.0, 173.0, 162.7, 158.4, 135.7 (CH), 129.1, 125.2, 114.6, 108.5 (CH), 66.9 (CH₂), 58.4 (CH₂), 56.7 (Me), 53.7 (CH₂), 52.0 (Me), 46.8 (CH₂); m/z (ESI) 371 (M+Na⁺, 100%).

Methyl 6-ethoxy-1-(2-morpholinoethyl)-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28g

Prepared by general procedure 1 from 2-bromo-6-ethoxy-1,4-benzoquinone 26c (0.924 g, 4.0 mmol), methyl 3-[(2-morpholinoethyl)amino]acrylate 27e (0.856 g, 4.0 mmol, copper acetate monohydrate (1.596 g, 8.0 mmol) and potassium carbonate (1.656 g, 12.0 mmol) stirred at reflux in acetonitrile (40 mL) for 15 h. Column chromatography eluting with ethyl acetate gave the title compound as a red oil (0.512 g, 37%); (Found: M+H⁺, 363.1245. C₁₈H₂₃N₂O₆ requires 363.1551); ν_max (CHCl₃)/cm⁻¹ 3008, 2953, 1732, 1688, 1643, 1603; δ_H (400 MHz; CDCl₃) 7.51 (1H, s, CH), 5.69 (1H, s, CH), 4.51 (2H, t, J 6.4, CH₂), 4.04 (2H, q, J 7.0, CH₂), 3.91 (3H, s, Me), 3.69 (4H, t, J 4.6, CH₂), 2.74 (2H, t, J 7.0, CH₂), 2.52 (4H, t, J 4.6, CH₂), 1.52 (3H, t, J 7.0, Me); δ_C (75 MHz; CDCl₃) 179.5, 175.3, 163.2, 159.9, 134.3 (CH), 130.6, 122.0, 114.8, 106.2 (CH), 66.9 (CH₂), 65.6 (CH₂), 58.5 (CH₂), 53.7 (CH₂), 51.9 (Me), 46.5 (CH₂), 13.9 (Me); m/z (ESI) 363 (M+H⁺, 100%).

Methyl 5-methoxy-6-methyl-1-(2-morpholinoethyl)-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28h

Prepared by general procedure 1 from 5-bromo-2-methoxy-3-methyl-1,4-benzoquinone 26d (0.693 g, 3.0 mmol), methyl 3-[(2-morpholinoethyl)amino]acrylate 27e (0.552 g, 3.0 mmol, copper acetate monohydrate (1.197 g, 6.0 mmol) and potassium carbonate (1.242 g, 9.0 mmol) stirred at reflux in acetonitrile for 16 h. Column chromatography eluting with ethyl acetate and methanol (49:1) gave the title compound as a red oil (0.468 g, 43%); (Found: M+H⁺, 363.1537. C₁₈H₂₃N₂O₆ requires 363.1551); ν_max (CHCl₃)/cm⁻¹ 3006, 1731, 1602; δ_H (400 MHz; CDCl₃) 7.48 (1H, s, CH), 4.49 (2H, t, J 6.4, CH₂), 4.10 (3H, s, Me), 3.91 (3H, s, Me), 3.69 (4H, t, J 4.5, CH₂), 2.73 (2H, t, J 6.4, CH₂), 2.52 (4H, t, J 4.5, CH₂), 1.97 (3H, s, Me); δ_C (75 MHz; CDCl₃) 180.0, 177.0, 162.8, 157.3, 134.5 (CH), 130.6, 126.9, 122.6, 114.3, 66.8 (CH₂), 61.3 (Me), 58.4 (CH₂), 53.6 (CH₂), 51.9 (Me), 46.6 (CH₂), 8.5 (Me); m/z (ESI) 363 (M+H⁺, 100%).

Methyl 1-methyl-4,9-dioxo-1H-benz[f]indole-3-carboxylate 28i

Prepared by general procedure 1 from methyl 3-(methylamino)acrylate 27a (49.0 mg, 0.422 mmol), 2-bromo-1,4-naphthoquinone 26e (100 mg, 0.422 mmol), copper(II) acetate monohydrate (126 mg, 0.633 mmol) and potassium carbonate (175 mg, 1.27 mmol) stirred at reflux in acetonitrile (5 mL). Column chromatography eluting with ethyl acetate and dichloromethane (1:19) gave the title compound as a yellow-orange solid (58.0 mg, 51%); mp 195–197 °C; (Found: M+Na⁺, 292.0580. C₁₅H₁₁NO₄Na requires 292.0580); ν_max (CHCl₃)/cm⁻¹ 3008, 1737, 1664, 1601, 1272, 1106, 930; δ_H (400 MHz; CDCl₃) 8.23-8.21 (1H, m, ArH), 8.15-8.13 (1H, m, ArH), 7.74-7.67 (2H, m, ArH), 7.51 (1H, s, CH), 4.13 (3H, s, Me), 3.93 (3H, s, Me); δ_C (100 MHz; CDCl₃) 179.0, 177.1, 162.9, 136.0 (CH), 134.3, 133.7 (CH), 133.0 (CH), 132.6, 132.3, 127.2 (CH), 126.1 (CH), 125.9, 115.0, 52.0 (Me), 37.6 (Me).

3-Hydroxymethyl-5-methoxy-1-methyl-1H-indole-4,7-dione 29a

Prepared by general procedure 2 from methyl 5-methoxy-1-methyl-4,7-dioxo-1H-indole-3-carboxylate 28a (43.8 mg, 0.176 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:9) gave the title compound as an orange solid (8.00 mg, 21%); mp 185–187 °C (lit.,²⁶ mp 186–187 °C); (Found: M+Na⁺, 244.0572. C₁₁H₁₁NO₄Na requires 244.0580); ν_max (CHCl₃)/cm⁻¹ 3692, 3009, 1645, 1600, 1509, 1177, 1036, 1017; δ_H (400 MHz; CDCl₃) 6.71 (1H, s, CH), 5.68 (1H, s, CH), 4.64 (2H, d, J 5.8, CH₂), 3.93 (3H, s, Me), 3.84 (3H, s, Me); δ_C (100 MHz; CDCl₃) 178.8, 178.7, 160.3, 130.4, 127.4 (CH), 125.9, 122.1, 107.0 (CH), 56.8 (CH₂), 56.6 (Me), 36.1 (Me).

3-Hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b

Prepared by general procedure 2 from methyl 6-methoxy-1-methyl-4,7-dioxo-1H-indole-3-carboxylate 28b (1.00 g, 4.01 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (2:3) gave the title compound as an orange solid (0.528 g, 60%); mp 228–230 °C; (Found: M+Na⁺, 244.0578. C₁₁H₁₁NO₄Na requires 244.0580); ν_max (CHCl₃)/cm⁻¹ 3416, 1670, 1629, 1601, 1337, 1035; δ_H (400 MHz; DMSO-d₆) 7.19 (1H, s, CH), 5.74 (1H, s, CH), 5.00 (1H, t, J 5.5, OH), 4.57 (2H, d, J 5.5, CH₂), 3.87 (3H, s, Me), 3.85 (3H, s, Me); δ_C (100 MHz; DMSO-d₆) 184.0, 171.5, 160.2, 131.1 (CH), 127.8, 126.7, 122.8, 107.3 (CH), 57.0 (Me), 56.3 (CH₂), 36.5 (Me).

3-Hydroxymethyl-6-methoxy-1-[2-(4-methoxyphenoxy)ethyl]-1H-indole-4,7-dione 29c

Prepared by general procedure 2 from methyl 6-methoxy-1-[2-(4-methoxyphenoxy)ethyl]-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28c (1.600 g, 4.16 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:5) gave recovered methyl ester (0.207 g, 13%) and the title compound as an orange solid (0.813 g, 56%; 64% brsm), mp 178–180 °C; (Found: M+Na⁺, 380.1101. C₁₉H₁₉NO₆Na requires 380.1105);ν _max (CHCl₃)/cm⁻¹ 3008, 1667, 1631, 1601, 1508; δ_H (400 MHz; CDCl₃) 7.02 (1H, s, CH), 6.83 (2H, d, J 9.1, ArH), 6.79 (2H, d, J 9.1, ArH), 5.78 (1H, s, CH), 4.68 (2H, t, J 5.0, CH₂), 4.65 (2H, d, J 6.9, CH₂), 4.26 (1H, t, J 6.9, OH), 4.25 (2H, t, J 5.0, CH₂), 3.87 (3H, s, Me), 3.77 (3H, s, Me); δ_C (75 MHz; CDCl₃) 185.1, 171.8, 160.3, 154.3, 152.1, 130.0 (CH), 127.7, 125.9, 125.6, 115.5 (CH), 114.7 (CH), 106.8 (CH), 67.2 (CH₂), 56.9 (CH₂), 56.8 (Me), 55.7 (Me), 48.7 (CH₂); m/z (ESI) 380 (M+Na⁺, 100%).

3-Hydroxymethyl-6-methoxy-1-[3-(4-methoxyphenoxy)propyl]-1H-indole-4,7-dione 29d

Prepared by general procedure 2 from methyl 6-methoxy-1-[3-(4-methoxyphenoxy)propyl]-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28d (0.890 g, 2.2 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:5) gave the title compound as an orange solid (0.284 g, 34%), mp 121–123 °C; (Found: M+Na⁺, 394.1260. C₂₀H₂₁NO₆Na requires 394.1261); ν_max (CHCl₃)/cm⁻¹ 3690, 3011, 1669, 1630, 1602, 1508; δ_H (400 MHz; CDCl₃) 6.87-6.82 (5H, m, ArH + CH), 5.78 (1H, s, CH), 4.61 (2H, d, J 6.9, CH₂), 4.52 (2H, t, J 6.8, CH₂), 4.29 (1H, t, J 6.9, OH), 3.93 (2H, t, J 5.6, CH₂), 3.87 (3H, s, Me), 3.80 (3H, s, Me), 2.26 (2H, tt, J 6.8, 5.6, CH₂); δ_C (75 MHz; CDCl₃) 185.1, 171.5, 160.3, 154.1, 152.5, 129.1 (CH), 128.0, 125.9, 125.5, 115.4 (CH), 114.7 (CH), 106.8 (CH), 64.7 (CH₂), 56.9 (CH₂), 56.8 (Me), 55.7 (Me), 46.4 (CH₂), 30.1 (CH₂); m/z (ESI) 394 (M+Na⁺, 100%).

1-[2-(Dimethylamino)ethyl]-3-hydroxymethyl-6-methoxy-1H-indole-4,7-dione 29e

Prepared by general procedure 2 from methyl 1-[2-(dimethylamino)ethyl]-6-methoxy-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28e (1.031 g, 3.37 mmol). Column chromatography eluting with methanol, ethyl acetate and triethylamine (8:1:0.01) gave the title compound as an orange oil (0.210 g, 22%); (Found: M+Na⁺, 301.1157. C₁₄H₁₈N₂O₄Na requires 301.1159); ν_max (CHCl₃)/cm⁻¹ 3011, 1668, 1630, 1602, 1505; δ_H (400 MHz; CDCl₃) 6.93 (1H, s, CH), 5.75 (1H, s, CH), 4.63 (2H, s, CH₂), 4.40 (2H, t, J 6.6, CH₂), 3.85 (3H, s, Me), 2.66 (2H, t, J 6.6, CH₂), 2.29 (6H, s, Me); δ_C (75 MHz; CDCl₃) 185.1, 171.5, 160.3, 129.0 (CH), 127.9, 126.0, 125.2, 106.7 (CH), 60.5 (CH₂), 56.9 (CH₂), 56.8 (Me), 46.9 (CH₂), 45.4 (Me); m/z (ESI) 279 (M+H⁺, 100%).

3-Hydroxymethyl-6-methoxy-1-(2-morpholinoethyl)-1H-indole-4,7-dione 29f

Prepared by general procedure 2 from methyl 6-methoxy-1-(2-morpholinoethyl)-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28f (0.560 g, 1.61 mmol). Column chromatography eluting with methanol, ethyl acetate and triethylamine (1:14:0.1) gave the title compound as a yellow solid (0.211 g, 41%), mp 128–130 °C; (Found: M+Na⁺, 321.1445. C₁₆H₂₁N₂O₅ requires 321.1445); ν_max (CHCl₃)/cm⁻¹ 3009, 2968, 1668, 1630, 1601, 1505; δ_H (400 MHz; CDCl₃) 6.92 (1H, s, CH), 5.79 (1H, s, CH), 4.65 (2H, d, J 6.9, CH₂), 4.44 (2H, t, J 6.6, CH₂), 4.28 (1H, t, J 6.9, OH), 3.88 (3H, s, Me), 3.70 (4H, t, J 4.6, CH₂O), 2.73 (2H, t, J 6.6, CH₂), 2.55 (4H, t, J 4.6, CH₂); δ_C (75 MHz; CDCl₃) 185.1, 171.6, 160.3, 128.8 (CH), 128.1, 126.0, 125.3, 106.8 (CH), 67.0 (CH₂), 58.7 (CH₂), 56.9 (CH₂), 56.8 (Me), 53.7 (CH₂), 46.2 (CH₂); m/z (ESI) 321 (M+H⁺, 100%), 343 (M+Na⁺, 62).

6-Ethoxy-3-hydroxymethyl-1-(2-morpholinoethyl)-1H-indole-4,7-dione 29g

Prepared by general procedure 2 from methyl 6-ethoxy-1-(2-morpholinoethyl)-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28g (0.503 g, 1.45 mmol). Column chromatography eluting with ethyl acetate and methanol (49:1) gave the title compound as an orange oil (0.183 g, 38%); (Found: M+H⁺, 335.1583. C₁₇H₂₃N₂O₅ requires 335.1601); ν_max (CHCl₃)/cm⁻¹ 3690, 3011, 1663, 1639, 1598, 1506; δ_H (400 MHz; CDCl₃) 6.83 (1H, s, CH), 5.65 (1H, s, CH), 4.65 (2H, s, CH₂), 4.43 (2H, t, J 6.5, CH₂), 4.03 (2H, q, J 7.0, CH₂), 3.69 (4H, t, J 4.6, CH₂), 2.71 (2H, t, J 6.5, CH₂), 2.52 (4H, t, J 4.6, CH₂), 1.52 (3H, t, J 7.0, Me); δ_C (75 MHz; CDCl₃) 179.0, 159.4, 130.0, 128.8, 126.8, 126.0 (CH), 122.3, 107.5 (CH), 66.9 (CH₂), 65.5 (CH₂), 58.7 (CH₂), 56.9 (CH₂), 53.7 (CH₂), 45.7 (CH₂), 13.9 (Me); m/z (ESI) 335 (M+H⁺, 100%).

3-Hydroxymethyl-5-methoxy-6-methyl-1-(2-morpholinoethyl)-1H-indole-4,7-dione 29h

Prepared by general procedure 2 from methyl 5-methoxy-6-methyl-1-(2-morpholinoethyl)-4,7-dioxo-4,7-dihydro-1H-indole-3-carboxylate 28h (0.461 g, 1.27 mmol). Column chromatography eluting with ethyl acetate and methanol (19:1) gave the title compound as an orange oil (0.233 g, 55%); (Found: M+H⁺, 335.1597. C₁₇H₂₃N₂O₅ requires 335.1601); ν_max (CHCl₃)/cm⁻¹ 3011, 2965, 1640, 1509; δ_H (400 MHz; CDCl₃) 6.81 (1H, s, CH), 4.63 (2H, s, CH₂), 4.40 (2H, t, J 6.6, CH₂), 4.01 (3H, s, Me), 3.68 (4H, t, J 4.6, CH₂), 2.69 (2H, t, J 6.6, CH₂), 2.51 (4H, t, J 4.6, CH₂), 1.97 (3H, s, Me); δ_C (75 MHz; CDCl₃) 180.6, 179.1, 156.6, 129.7, 129.6, 127.2 (CH), 125.7, 122.7, 66.9 (CH₂), 61.2 (Me), 58.6 (CH₂), 56.9 (CH₂), 53.7 (CH₂), 45.9 (CH₂), 8.8 (Me); m/z (ESI) 335 (M+H⁺, 100%).

3-Hydroxymethyl-1-methyl-1H-benz[f]indole-4,9-dione 29i

Prepared by general procedure 2 from methyl 1-methyl-4,9-dioxo-1H-benz[f]indole-3-carboxylate 28i (0.461 g, 1.71 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:4) gave the title compound as a yellow solid (0.151 g, 37%); mp 219–221 °C; (Found: M+Na⁺, 264.0633. C₁₄H₁₁NO₃Na requires 264.0631); ν_max (CHCl₃)/cm⁻¹ 3007, 1650, 1593, 1506, 1260, 929; δ_H (400 MHz; CDCl₃) 8.18-8.14 (2H, m, ArH), 7.72-7.69 (2H, m, ArH), 6.85 (1H, s, CH), 4.72 (2H, d, J 6.9, CH₂), 4.36 (1H, t, J 6.9, OH), 4.07 (3H, s, Me); δ_C (100 MHz; CDCl₃) 182.8, 176.2, 133.7, 133.6, 133.4 (CH), 133.3 (CH), 131.6, 129.1 (CH), 126.6 (CH), 126.5 (CH), 126.1, 125.9, 56.9 (CH₂), 36.6 (Me).

5-Methoxy-1-methyl-3-(4-nitrophenoxy)methyl-1H-indole-4,7-dione 1

Prepared from 3-hydroxymethyl-5-methoxy-1-methyl-1H-indole-4,7-dione 29a as previously described.²⁷

6-Methoxy-1-methyl-3-(4-nitrophenoxy)methyl-1H-indole-4,7-dione 2

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (111 mg, 0.50 mmol) and 4-nitrophenol (348 mg, 2.50 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:49) gave the title compound as a yellow solid (151 mg, 89%); mp 225–227 °C; (Found: M+Na⁺, 365.0750. C₁₇H₁₄N₂O₆Na requires 365.0744); ν_max (CHCl₃)/cm⁻¹ 2360, 1671, 1644, 1596, 1515, 1343; δ_H (400 MHz; CDCl₃) 8.22 (2H, d, J 7.1, ArH), 7.06 (2H, d, J 7.1, ArH), 6.99 (1H, s, CH), 5.77 (1H, s, CH), 5.41 (2H, s, CH₂), 4.00 (3H, s, Me), 3.86 (3H, s, Me); δ_C (100 MHz; CDCl₃) 183.8, 172.0, 163.4, 160.0, 141.8, 130.2 (CH), 128.2, 126.0 (CH), 123.6, 119.7, 114.8 (CH), 107.3 (CH), 63.1 (CH₂), 56.7 (Me), 36.7 (Me); m/z (ESI) 365 (M+Na⁺, 100%); HPLC: purity (AUC) 100%.

5-Methoxy-1-methyl-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 3

Prepared by general procedure 3 from 3-hydroxymethyl-5-methoxy-1-methyl-1H-indole-4,7-dione 29a (145 mg, 0.66 mmol) 2,4,6-trifluorophenol (485 mg, 3.28 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:24) gave the title compound as a yellow solid (195 mg, 85%); mp 182–184 °C; (Found: M+Na⁺, 374.0617. C₁₇H₁₂NO₄F₃Na requires 374.0611); ν_max (CHCl₃)/cm⁻¹ 3011, 1676, 1645, 1601, 1509; δ_H (400 MHz; CDCl₃) 6.99 (1H, s, CH), 6.70 (2H, t, J 8.4, ArH), 5.69 (1H, s, CH), 5.33 (2H, s, CH₂), 3.99 (3H, s, Me), 3.84 (3H, s, Me); δ_C (100 MHz; CDCl₃) 179.1, 177.4, 160.3, 157.3 (dt, J 244, 14), 156.2 (ddd, J 250, 15, 8), 132.2 (dt, J 15, 5), 129.8, 129.0 (CH), 121.1, 120.7, 106.8 (CH), 100.7 (ddd, J 28, 27, 8, CH), 68.5 (CH₂), 56.5 (Me), 36.3 (Me); m/z (ESI) 374 (M+Na⁺, 100%); HPLC: purity (AUC) 99.7%.

6-Methoxy-1-methyl-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 4

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (96 mg, 0.43 mmol) and 2,4,6-trifluorophenol (321 mg, 2.17 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:39) gave the title compound as a yellow solid (136 mg, 89%); mp 188–190 °C; (Found: M+Na⁺, 374.0623. C₁₇H₁₂NO₄F₃Na requires 374.0611); ν_max (CHCl₃)/cm⁻¹ 3012, 1670, 1645, 1602, 1510; δ_H (400 MHz; CDCl₃) 7.09 (1H, s, CH), 6.71 (2H, t, J 8.4, ArH), 5.72 (1H, s, CH), 5.34 (2H, s, CH₂), 4.02 (3H, s, Me), 3.84 (3H, s, Me); δ_C (100 MHz; CDCl₃) 183.5, 172.1, 159.8, 157.3 (dt, J 245, 15), 156.2 (ddd, J 250, 15, 8), 132.2 (dt, J 15, 5), 130.7 (CH), 128.1, 123.7, 120.6, 107.2 (CH), 100.7 (ddd, J 28, 27, 8, CH), 68.7 (CH₂), 56.6 (Me), 36.3 (Me); m/z (ESI) 374 (M+Na⁺, 100%); HPLC: purity (AUC) 90.3%.

6-Methoxy-1-methyl-3-phenoxymethyl-1H-indole-4,7-dione 5

Prepared by a variation of general procedure 2 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (50 mg, 0.23 mmol), phenol (106 mg, 1.13 mmol) and sodium hydride (60% in mineral oil; 45 mg, 1.13 mmol) in place of potassium carbonate. Column chromatography eluting with ethyl acetate and dichloromethane (1:9) gave the title compound as a yellow solid (21 mg, 31%); mp 147–149 °C; (Found: M+Na⁺, 320.0891. C₁₇H₁₅NO₄Na requires 320.0893); ν_max (CHCl₃)/cm⁻¹ 3012, 1669, 1643, 1600, 1240, 1032; δ_H (400 MHz; CDCl₃) 7.31-7.26 (2H, m, ArH), 7.01-6.98 (1H, m, CH), 6.97-6.94 (3H, m, ArH), 5.72 (1H, s, CH), 5.30-5.28 (2H, m, CH₂), 3.95 (3H, s, Me), 3.82 (3H, s, Me); δ_C (100 MHz; CDCl₃) 183.8, 171.9, 159.9, 158.4, 130.2 (CH), 129.5 (CH), 128.0, 123.4, 121.6, 121.0 (CH), 114.7 (CH), 107.2 (CH), 62.5 (CH₂), 56.6 (Me), 36.5 (Me); HPLC: purity (AUC) 100%.

5-Methoxy-1-methyl-3-(4-methylsulfonylphenoxy)methyl-1H-indole-4,7-dione 6

Prepared by general procedure 3 from 3-hydroxymethyl-5-methoxy-1-methyl-1H-indole-4,7-dione 29a (50 mg, 0.23 mmol) and 4-methylsulfonylphenol (272 mg, 1.58 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (2:3) gave the title compound as a yellow solid (61 mg, 72%); mp 196–198 °C; (Found: M+Na⁺, 398.0655. C₁₈H₁₇NO₆SNa requires 398.0669); ν_max (CHCl₃)/cm⁻¹ 3012, 1674, 1646, 1599, 1318, 1147; δ_H (400 MHz; CDCl₃) 7.88-7.86 (2H, m, ArH), 7.12-7.09 (2H, m, ArH), 6.87 (1H, s, CH), 5.71 (1H, s, CH), 5.36 (2H, s, CH₂), 3.96 (3H, s, Me), 3.84 (3H, s, Me), 3.04 (3H, s, Me); δ_C (100 MHz; CDCl₃) 178.9, 177.7, 162.5, 160.3, 132.6, 129.9, 129.6 (CH), 128.5 (CH), 121.0, 120.1, 115.3 (CH), 106.9 (CH), 62.8 (CH₂), 56.6 (Me), 44.8 (Me), 36.4 (Me); HPLC: purity (AUC) 93.5%.

6-Methoxy-1-methyl-3-(4-methylsulfonylphenoxy)methyl-1H-indole-4,7-dione 7

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (50.0 mg, 0.226 mmol) and 4-methylsulfonylphenol (195 mg, 1.13 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:9) gave the title compound as a yellow solid (20 mg, 24%); mp 240–242 °C; (Found: M+Na⁺, 398.0669. C₁₈H₁₇NO₆SNa requires 398.0669); ν_max (CHCl₃)/cm⁻¹ 3012, 1671, 1644, 1599, 1340, 1146; δ_H (400 MHz; CDCl₃) 7.89-7.86 (2H, m, ArH), 7.13-7.09 (2H, m, ArH), 6.97 (1H, s, CH), 5.75 (1H, s, CH), 5.37 (2H, s, CH₂), 3.99 (3H, s, Me), 3.84 (3H, s, Me), 3.04 (3H, s, Me); δ_C (100 MHz; CDCl₃) 183.8, 172.0, 162.5, 160.0, 132.6, 130.2 (CH), 129.6 (CH), 128.1, 123.5, 119.9, 115.2 (CH), 107.2 (CH), 62.8 (CH₂), 56.7 (Me), 44.8 (Me), 36.7 (Me); HPLC: purity (AUC) 90.6%.

4-[(6-Methoxy-1-methyl-4,7-dioxo-1H-indol-3-yl)methoxy]benzoic acid 8

Prepared by a variation of general procedure 3 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (50 mg, 0.23 mmol), 4-hydroxybenzoic acid (31 mg, 0.23 mmol) and sodium hydride (60% in mineral oil; 45 mg, 1.13 mmol) in place of potassium carbonate. Column chromatography eluting with methanol and dichloromethane (3:97) gave the title compound as a yellow solid (28 mg, 36%); mp 198–200 °C; (Found: M+Na⁺, 364.0782. C₁₈H₁₅NO₆Na requires 364.0792); ν_max (CHCl₃)/cm⁻¹ 3691, 3601, 3011, 1708, 1669, 1645, 1602, 1512, 1270, 1165, 1037, 909; δ_H (400 MHz; DMSO-d₆) 10.34 (1H, br s, CO₂H), 7.83 (2H, d, J 8.8, ArH), 7.43 (1H, s, CH), 6.84 (2H, d, J 8.8, ArH), 5.82 (1H, s, CH), 5.33 (2H, s, CH₂), 3.90 (3H, s, Me), 3.77 (3H, s, Me); δ_C (100 MHz; DMSO-d₆) 183.3, 171.3, 165.4, 162.1, 159.8, 131.9 (CH), 131.6 (CH), 127.7, 123.1, 120.2, 118.5, 115.4 (CH), 107.1 (CH), 58.0 (CH₂), 56.7 (Me), 36.2 (Me); HPLC: purity (AUC) 94.6%.

3-Fluoro-4-[(6-methoxy-1-methyl-4,7-dioxo-1H-indol-3-yl)methoxy]benzoic acid 9

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (20 mg, 0.09 mmol) and 3-fluoro-4-hydroxybenzoic acid (71 mg, 0.45 mmol). Column chromatography eluting with methanol and dichloromethane (1:19) gave the title compound as a yellow solid (14.0 mg, 43%); mp 220–222 °C; (Found: M+Na⁺, 382.0682. C₁₈H₁₄¹⁹FNO₆Na requires 382.0697); ν_max (CHCl₃)/cm⁻¹ 3691, 3572, 3002, 1714, 1670, 1646, 1602, 1514, 1340, 1286, 1037, 909; δ_H (400 MHz; DMSO-d₆) 10.88 (1H, br s, CO₂H), 7.69-7.66 (2H, m, ArH), 7.47 (1H, s, CH), 7.07-7.02 (1H, m, ArH), 5.83 (1H, s, CH), 5.35 (2H, s, CH₂), 3.90 (3H, s, Me), 3.77 (3H, s, Me); δ_C (100 MHz; DMSO-d₆) 183.7, 171.7, 165.0, 160.2, 150.9 (d, J 242), 150.4 (d, J 12), 132.3 (CH), 128.2, 127.3 (CH), 123.5, 121.1 (d, J 7), 118.6, 118.0 (CH), 117.5 (d, J 20, CH), 107.5 (CH), 58.9 (CH₂), 57.1 (Me), 36.6 (Me); HPLC: purity (AUC) 94.8%.

3-(2,5-Dioxopyrrolidin-1-yl)methyl-6-methoxy-1-methyl-1H-indole-4,7-dione 10

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (50.0 mg, 0.226 mmol) and succinimide (112 mg, 1.13 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (2:3) gave the title compound as a yellow solid (26.0 mg, 40%); mp 275–277 °C; (Found: M+Na⁺, 325.0785. C₁₅H₁₄N₂O₅Na requires 325.0795); ν_max (CHCl₃)/cm⁻¹ 1707, 1669, 1645, 1602, 909; δ_H (400 MHz; CDCl₃) 6.75 (1H, s, CH), 5.70 (1H, s, CH), 4.90 (2H, s, CH₂), 3.92 (3H, s, Me), 3.81 (3H, s, Me), 2.76 (4H, s, CH₂); δ_C (100 MHz; CDCl₃) 183.5, 176.8, 172.1, 159.6, 130.6 (CH), 128.1, 123.8, 119.0, 107.5 (CH), 56.6 (Me), 36.6 (Me), 33.9 (CH₂), 28.2 (CH₂); HPLC: purity (AUC) 96.9%.

3-(2,5-Dioxopyrrolidin-1-yloxy)methyl-5-methoxy-1-methyl-1H-indole-4,7-dione 11

Prepared by general procedure 3 from 3-hydroxymethyl-5-methoxy-1-methyl-1H-indole-4,7-dione 29a (50 mg, 0.23 mmol) and N-hydroxysuccinimide (130 mg, 1.13 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:4) gave the title compound as a yellow solid (24 mg, 34%); mp 194–196 °C; (Found: M+Na⁺, 341.0737. C₁₅H₁₄N₂O₆Na requires 341.0744); ν_max (CHCl₃)/cm⁻¹ 1729, 1673, 1646, 1602, 1512, 1192; δ_H (400 MHz; CDCl₃) 7.02 (1H, s, CH), 5.66 (1H, s, CH), 5.27 (2H, s, CH₂), 3.96 (3H, s, Me), 3.81 (3H, s, Me), 2.68 (4H, s, CH₂); δ_C (100 MHz; CDCl₃) 178.9, 177.8, 171.3, 160.2, 130.8 (CH), 130.1, 121.6, 117.8, 106.8 (CH), 69.6 (CH₂), 56.6 (Me), 36.4 (Me), 25.5 (CH₂); HPLC: purity (AUC) 94.5%.

3-(2,5-Dioxopyrrolidin-1-yloxy)methyl-6-methoxy-1-methyl-1H-indole-4,7-dione 12

Prepared by general procedure 4 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (50 mg, 0.23 mmol) and N-hydroxysuccinimide (130 mg, 1.13 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (2:3) gave the title compound as a yellow solid (60 mg, 83%); mp 255–257 °C; (Found: M+Na⁺, 341.0731. C₁₅H₁₄N₂O₆Na requires 341.0744); ν_max (CHCl₃)/cm⁻¹ 1729, 1671, 1644, 1603, 909; δ_H (400 MHz; CDCl₃) 7.11 (1H, s, CH), 5.67 (1H, s, CH), 5.28 (2H, s, CH₂), 3.99 (3H, s, Me), 3.82 (3H, s, Me), 2.67 (4H, s, CH₂); δ_C (100 MHz; CDCl₃) 183.8, 172.1, 171.3, 159.8, 132.6 (CH), 128.3, 124.4, 117.6, 107.2 (CH), 69.4 (CH₂), 56.6 (Me), 36.7 (Me), 25.5 (CH₂); HPLC: purity (AUC) 99.0%.

3-(2H-1,2,3-Triazol-2-yl)methyl-6-methoxy-1-methyl-1H-indole-4,7-dione 14 and 3-(1H-1,2,3-triazol-1-yl)methyl-6-methoxy-1-methyl-1H-indole-4,7-dione 13

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (20 mg, 0.09 mmol) and 1,2,3-triazole (0.03 mL, 0.45 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (2:3) gave the title compounds 14 and 13 as yellow solids (8 mg, 33%; 11 mg, 45% respectively); 14: mp 210–212 °C; (Found: M+Na⁺, 295.0793. C₁₃H₁₂N₄O₃Na requires 295.0802); ν_max (CHCl₃)/cm⁻¹ 3011, 1670, 1645, 1601, 1189, 1036; δ_H (400 MHz; CDCl₃) 7.65 (2H, s, triazole-H), 6.61 (1H, s, CH), 5.86 (2H, s, CH₂), 5.74 (1H, s, CH), 3.92 (3H, s, Me), 3.83 (3H, s, Me); δ_C (100 MHz; CDCl₃) 183.6, 172.1, 159.8, 134.4 (CH), 130.5 (CH), 128.1, 123.6, 118.9, 107.4 (CH), 56.6 (Me), 49.8 (CH₂), 36.6 (Me); HPLC: purity (AUC) 93.9%. 13: mp 268–270 °C; (Found: M+Na⁺, 295.0789. C₁₃H₁₂N₄O₃Na requires 295.0802); ν_max (CHCl₃)/cm⁻¹ 3011, 1672, 1644, 1602, 1192, 1036; δ_H (400 MHz; CDCl₃) 7.83 (1H, d, J 0.8, triazole-H), 7.67 (1H, d, J 0.8, triazole-H), 6.91 (1H, s, CH), 5.74 (1H, s, CH), 5.72 (2H, s, CH₂), 3.94 (3H, s, Me), 3.84 (3H, s, Me); δ_C (100 MHz; CDCl₃) 184.0, 172.0, 160.0, 143.4, 133.8 (CH), 131.5 (CH), 128.0, 124.2 (CH), 118.3, 107.3 (CH), 56.7 (Me), 44.3 (CH₂), 36.7 (Me); HPLC: purity (AUC) 97.7%.

3-(2H-Tetrazol-2-yl)methyl-6-methoxy-1-methyl-1H-indole-4,7-dione 16 and 3-(1H-tetrazol-1-yl)methyl-6-methoxy-1-methyl-1H-indole-4,7-dione 15

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-methyl-1H-indole-4,7-dione 29b (74.0 mg, 0.34 mmol) and tetrazole (0.45 M in acetonitrile; 6 mL, 2.68 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:4) gave the title compounds 16 and 15 were obtained as yellow solids (20 mg, 22%; 33 mg, 36% respectively); 16: mp 198–200 °C; (Found: M+Na⁺, 296.0745. C₁₂H₁₁N₅O₃Na requires 296.0754); ν_max (CHCl₃)/cm⁻¹ 2959, 2931, 2872, 2337, 1710, 1673, 1646, 1602, 1515, 1195, 1036; δ_H (400 MHz; CDCl₃) 8.51 (1H, s, N=CHN), 6.78 (1H, s, CH), 6.05 (2H, s, CH₂), 5.74 (1H, s, CH), 3.94 (3H, s, Me), 3.82 (3H, s, Me); δ_C (100 MHz; CDCl₃) 183.4, 172.1, 159.8, 152.9 (CH), 130.9 (CH), 128.2, 123.6, 116.1, 107.3 (CH), 56.7 (Me), 47.7 (CH₂), 36.6 (Me); HPLC: purity (AUC) 90.0 %. 15: mp 230–232 °C; (Found: M+Na⁺, 296.0748. C₁₂H₁₁N₅O₃Na requires 296.0754); ν_max (CHCl₃)/cm⁻¹ 2960, 2929, 2873, 2361, 2342, 1733, 1675, 1643, 1602, 1459, 1036; δ_H (400 MHz; CDCl₃) 8.93 (1H, s, NCH=N), 7.03 (1H, s, CH), 5.75 (1H, s, CH), 5.72 (2H, s, CH₂), 3.98 (3H, s, Me), 3.85 (3H, s, Me); δ_C (100 MHz; CDCl₃) 183.9, 172.0, 160.1, 143.0 (CH), 131.6 (CH), 126.2, 123.5, 116.2, 107.2 (CH), 56.8 (Me), 42.4 (CH₂), 36.7 (Me); HPLC: purity (AUC) 98.8%.

6-Methoxy-1-(2-(4-methoxyphenoxy)ethyl)-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 17

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-(2-(4-methoxyphenoxy)ethyl)-1H-indole-4,7-dione 29c (0.801 g, 2.24 mmol) and 2,4,6-trifluorophenol (1.658 g, 11.20 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:24) gave the title compound as a yellow solid (0.966 g, 93%), mp 134–136 °C; (Found: M+Na⁺, 510.1128. C₂₅H₂₀NO₅F₃Na requires 510.1135); ν_max (CHCl₃)/cm⁻¹ 3011, 1645, 1602, 1509; δ_H (400 MHz; CDCl₃) 7.29 (1H, s, CH), 6.84 (2H, d, J 9.1, ArH), 6.80 (2H, d, J 9.1, ArH), 6.66 (2H, t, J 8.4, ArH), 5.71 (1H, s, CH), 5.35 (2H, s, CH₂), 4.72 (2H, t, J 5.0, CH₂), 4.26 (2H, t, J 5.0, CH₂), 3.84 (3H, s, Me), 3.78 (3H, s, Me); δ_C (75 MHz; CDCl₃) 183.5, 172.1, 159.8, 157.3 (dt, J 245, 14, CF), 156.3 (ddd, J 250, 15, 8, CF) 154.3, 152.1, 132.2 (dt, J 15, 5, C) 131.6 (CH), 127.2, 124.3, 120.6, 115.6 (CH), 114.7 (CH), 107.2 (CH), 100.7 (ddd, J 27, 26, 8, CH), 68.6 (CH₂), 67.2 (CH₂), 56.7 (Me), 55.7 (Me), 48.9 (CH₂); m/z (ESI) 510 (M+Na⁺, 100%); HPLC: purity (AUC) 100%.

1-(2-Hydroxyethyl)-6-methoxy-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 18

A solution of cerium (IV) ammonium nitrate (2.74 g, 5.0 mmol) in water (10 mL) was added as a single portion to a stirred solution of 6-methoxy-1-(2-(4-methoxyphenoxy)ethyl)-3-((2,4,6-trifluorophenoxy)methyl)-1H-indole-4,7-dione 17 (0.924 g, 2.0 mmol) in DMF (20 mL), and the resulting mixture was stirred at room temperature for 15 h. Water (150 mL) was added, and the mixture was extracted with ethyl acetate (3 × 40 mL). The combined organic phases were washed with water (50 mL), dried (MgSO₄), filtered and concentrated. Column chromatography eluting with ethyl acetate and dichloromethane (1:3) gave the title compound as a yellow-orange solid (0.732 g, 96%), mp 143–145 °C; (Found: M+Na⁺, 404.0717. C₁₈H₁₄F₃NO₅Na requires 404.0716);ν_max (CHCl₃)/cm⁻¹ 3011, 1644, 1602, 1510; δ_H (400 MHz; CDCl₃) 7.24 (1H, s, CH), 6.69 (2H, t, J 8.3, ArH), 5.68 (1H, s, CH), 5.31 (2H, s, CH₂), 4.51 (2H, t, J 5.1, CH₂), 4.00 (2H, t, J 5.1, CH₂), 3.83 (3H, s, Me); δ_C (75 MHz; CDCl₃) 183.5, 172.2, 159.9, 157.4 (dt, J 246, 14), 156.2 (ddd, J 250, 15, 7), 132.3 (dt, J 15, 5), 131.3 (CH), 127.5, 124.2, 120.7, 107.2 (CH), 100.7 (ddd, J 27, 26, 8, CH), 68.6 (CH₂), 61.9 (CH₂), 56.7 (Me), 51.6 (CH₂); m/z (ESI) 404 (M+Na⁺, 100%); HPLC: purity (AUC) 97.6%.

6-Methoxy-1-(3-(4-methoxyphenoxy)propyl)-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-(3-(4-methoxyphenoxy)propyl)-1H-indole-4,7-dione 29d (0.266 g, 0.72 mmol) and 2,4,6-trifluorophenol (0.531 g, 3.58 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (1:49) gave the title compound as a yellow solid (0.316 g, 88%), mp 138–140 °C; (Found: M+Na⁺, 524.1280. C₂₆H₂₂F₃NO₆Na requires 524.1291); ν_max (CHCl₃)/cm⁻¹ 3009, 2938, 1668, 1644, 1602, 1509; δ_H (400 MHz; CDCl₃) 7.15 (1H, s, CH), 6.84 (4H, s, ArH), 6.67 (2H, t, J 8.4, ArH), 5.71 (1H, s, CH), 5.32 (2H, s, CH₂), 4.56 (2H, t, J 6.7, CH₂), 3.93 (2H, t, J 5.9, CH₂), 3.84 (3H, s, Me), 3.79 (3H, s, Me), 2.28 (2H, tt, J 6.7, 5.9, CH₂); δ_C (75 MHz; CDCl₃) 183.6, 171.8, 159.9, 157.4 (dt, J 245, 14), 156.6 (ddd, J 250, 15, 8), 154.1, 152.6, 132.0 (dt, J 15, 5) 130.7 (CH), 127.5, 124.2, 120.6, 115.5 (CH), 114.7 (CH), 107.1 (CH), 100.7 (ddd, J 27, 26, 8, CH), 68.5 (CH₂), 64.8 (CH₂), 56.6 (Me), 55.7 (Me), 46.6 (CH₂), 30.2 (CH₂); m/z (ESI) 524 (M+Na⁺, 100%).

1-(3-Hydroxypropyl)-6-methoxy-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 19

A solution of cerium(IV) ammonium nitrate (0.785 g, 1.43 mmol) in water (15 mL) was added to a stirred solution of 6-methoxy-1-(3-(4-methoxyphenoxy)propyl)-3-((2,4,6-trifluorophenoxy)methyl)-1H-indole-4,7-dione (0.287 g, 0.57 mmol) in DMF (15 mL), and the resulting mixture was stirred at room temperature for 1.5 h. Water (100 mL) was added and the mixture was extracted with ethyl acetate (3 × 25 mL). The combined organic phases were washed with water (25 mL), dried (MgSO₄), filtered and concentrated. Column chromatography eluting with ethyl acetate and dichloromethane (1:6) gave the title compound as a yellow solid (0.206 g, 92%), mp 129–131 °C; (Found: M+Na⁺, 418.088. C₁₉H₁₆F₃NO₅Na requires 418.0873); ν_max (CHCl₃)/cm⁻¹ 3690, 3011, 1644, 1602, 1510; δ_H (400 MHz; CDCl₃) 7.19 (1H, s, CH), 6.70 (2H, t, J 8.6, ArH), 5.72 (1H, s, CH), 5.34 (2H, s, CH₂), 4.50 (2H, t, J 6.6, NCH₂), 3.84 (3H, s, OMe), 3.65 (2H, t, J 5.6, CH₂OH), 2.07 (2H, m, CH₂), 1.90 (1H, br s, OH); δ_C (75 MHz; CDCl₃) 183.5, 172.1, 159.9, 157.4 (dt, J 246, 14), 156.3 (ddd, J 250, 15, 8), 132.2 (dt, J 15, 5), 131.7 (CH), 127.6, 124.1, 121.0, 107.1 (CH), 100.7 (ddd, J 27, 26, 8, CH), 68.6 (CH₂), 58.7 (CH₂), 56.7 (Me), 45.9 (CH₂), 33.4 (CH₂); m/z (ESI) 418 (M+Na⁺, 100%); HPLC: purity (AUC) 99.2%.

1-(2-(Dimethylamino)ethyl)-6-methoxy-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 20

Prepared by general procedure 3 from 1-(2-(dimethylamino)ethyl)-3-hydroxymethyl-6-methoxy-1H-indole-4,7-dione 29e (0.182 g, 0.65 mmol) and 2,4,6-trifluorophenol (0.484 g, 3.27 mmol). Column chromatography eluting with methanol and ethyl acetate (19:1) gave the title compound as an orange solid (0.142 g, 54%), mp 76–78 °C; (Found: M+Na⁺, 409.1369. C₂₀H₂₀F₃N₂O₄Na requires 409.1370); ν_max (CHCl₃)/cm⁻¹ 3011, 2957, 1644, 1602, 1510; δ_H (400 MHz; CDCl₃) 7.19 (1H, s, CH), 6.69 (2H, t, J 8.4, ArH), 5.71 (1H, s, CH), 5.34 (2H, s, CH₂O), 4.46 (2H, t, J 6.8, CH₂), 3.84 (3H, s, OMe), 2.71 (2H, t, J 6.8, CH₂), 2.33 (6H, s, Me); δ_C (75 MHz; CDCl₃) 183.6, 171.9, 159.9, 157.3 (dt, J 246, 14), 156.2 (ddd, J 250, 15, 7), 132.2 (dt, J 15, 5), 130.5 (CH), 127.4, 124.0, 120.7, 107.1 (CH), 100.7 (td, J 27, 8, CH), 68.6 (CH₂), 59.3 (CH₂), 56.6 (Me), 47.0 (CH₂), 45.5 (Me); m/z (ESI) 409 (M+H⁺, 100%); HPLC: purity (AUC) 97.0%.

6-Methoxy-1-(2-morpholinoethyl)-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 21

Prepared by general procedure 3 from 3-hydroxymethyl-6-methoxy-1-(2-morpholinoethyl)-1H-indole-4,7-dione 29f (0.208 g, 0.65 mmol) and 2,4,6-triifluorophenol (0.481 g, 3.25 mmol). Column chromatography eluting with ethyl acetate gave the title compound as a yellow solid (0.166 g, 57%), mp 101–103 °C; (Found: M+H⁺, 451.1496. C₂₂H₂₂N₂O₅F₃ requires 451.1475); ν_max (CHCl₃)/cm⁻¹ 3011, 1668, 1644, 1602, 1507; δ_H (400 MHz; CDCl₃) 7.20 (1H, s, CH), 6.70 (2H, t, J 8.4, ArH), 5.72 (1H, s, CH), 5.35 (2H, s, CH₂), 4.48 (2H, t, J 6.6, NCH₂), 3.84 (3H, s, OMe), 3.470 (4H, t, J 4.7, OCH₂), 2.75 (2H, t, J 6.6, CH₂N), 2.55 (4H, t, J 4.7, NCH₂); δ_C (75 MHz; CDCl₃) 183.6, 171.9, 159.9, 157.3 (dt, J 246, 14), 156.2 (ddd, J 250, 15, 7), 132.3 (dt, J 15, 5), 130.4 (CH), 127.5, 123.9, 120.8, 107.1 (CH), 100.7 (ddd, J 27, 26, 9, CH), 68.8 (CH₂), 66.9 (CH₂), 58.6 (CH₂), 56.7 (Me), 53.7 (CH₂), 46.4 (CH₂); m/z (ESI) 451 (M+H⁺, 100%); HPLC: purity (AUC) 99.0%.

6-Ethoxy-1-(2-morpholinoethyl)-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 22

Prepared by general procedure 3 from 6-ethoxy-3-hydroxymethyl-1-(2-morpholinoethyl)-1H-indole-4,7-dione 29g (0.172 g, 0.51 mmol) and 2,4,6-trifluorophenol (0.381 g, 2.57 mmol). Column chromatography eluting with ethyl acetate gave the title compound as an orange oil (0.162 g, 68%); (Found: M+H⁺, 565.1645. C₂₃H₂₄N₂O₅F₃ requires 465.1632); ν_max (CHCl₃)/cm⁻¹ 3045, 2999, 1674, 1639, 1599, 1509; δ_H (400 MHz; CDCl₃) 7.09 (1H, s, CH), 6.69 (2H, t, J 8.4, ArH), 5.63 (1H, s, CH), 5.33 (2H, s, CH₂), 4.487 (2H, t, J 6.6, CH₂), 4.00 (2H, q, J 7.0, CH₂), 3.70 (4H, t, J 4.6, CH₂), 2.73 (2H, t, J 6.6, CH₂), 2.53 (4H, t, J 4.6, CH₂), 1.49 (3H, t, J 7.0, Me); δ_C (75 MHz; CDCl₃) 179.2, 177.7, 159.4, 157.3 (dt, J 246, 15), 156.2 (ddd, J 250, 15, 8), 132.3 (dt, J 15, 5), 129.2, 128.4 (CH), 121.3, 120.8, 107.2 (CH), 100.7 (ddd, J 27, 26, 5), 68.6 (CH₂), 66.9 (CH₂), 65.3 (CH₂), 58.7 (CH₂), 53.7 (CH₂), 45.9 (CH₂), 13.9 (Me); m/z (ESI) 465 (M+H⁺, 100%); HPLC: purity (AUC) 98.0%.

5-Methoxy-6-methyl-1-(2-morpholinoethyl)-3-(2,4,6-trifluorophenoxy)methyl-1H-indole-4,7-dione 23

Prepared by general procedure 3 from 3-hydroxymethyl-5-methoxy-6-methyl-1-(2-morpholinoethyl)-1H-indole-4,7-dione 29h (0.218 g, 0.65 mmol) and 2,4,6-trifluorophenol (0.483 g, 3.26 mmol). Column chromatography eluting with ethyl acetate and dichloromethane (2:1) gave the title compound as a yellow solid (0.200 g, 66%), mp 94–96 °C; (Found: M+H⁺, 465.1642. C₂₃H₂₄N₂O₅F₃ requires 465.4417); ν_max (CHCl₃)/cm⁻¹ 3008, 1642, 1602, 1509; δ_H (400 MHz; CDCl₃) 7.07 (1H, s, CH), 6.69 (2H, t, J 8.4, ArH), 5.33 (2H, s, CH₂), 4.45 (2H, t, J 6.5, CH₂), 4.01 (3H, s, Me), 3.70 (4H, t, J 4.6, CH₂), 2.72 (2H, t, J 6.5, CH₂), 2.54 (4H, t, J 4.6, CH₂), 1.97 (3H, s, Me); δ_C (75 MHz; CDCl₃) 179.4, 179.3, 157.3 (dt, J 231, 14), 156.6, 156.2 (ddd, J 250, 15, 7), 132.2 (td, J 15, 5), 129.1, 128.8 (CH), 121.6, 120.3, 100.7 (ddd, J 27, 26, 8, CH), 68.5 (CH₂), 66.9 (CH₂), 61.1 (Me), 58.6 (CH₂), 53.7 (CH₂), 46.1 (CH₂), 8.73 (Me); one carbon unobserved; m/z (ESI) 465 (M+H⁺, 100%); HPLC: purity (AUC) 97.7%.

3-(2,5-Dioxopyrrolidin-1-yloxy)methyl-1-methyl-1H-benz[f]indole-4,9-dione 24

Prepared by general procedure 3 from 3-hydroxymethyl-1-methyl-1H-benz[f]indole-4,9-dione 29i (50.0 mg, 0.207 mmol) and N-hydroxysuccinimide (167 mg, 1.45 mmol). Column chromatography eluting with ethyl acetate-dichloromethane (2:8) gave the title compound as a yellow solid (56.0 mg, 80%); mp 223–225 °C; (Found: M+Na⁺, 361.0784. C₁₈H₁₄N₂O₅Na requires 361.0795); λ_max (acetonitrile)/nm 253 (log ε 4.47), 279 (4.18), 327 (3.75), 387 (3.50); ν_max (CHCl₃)/cm⁻¹ 3008, 1729, 1658, 1257; δ_H (400 MHz; CDCl₃) 8.16-8.11 (2H, m, H-5, H-8), 7.71-7.66 (2H, m, H-6, H-7), 7.18 (1H, s, H-2), 5.41 (2H, s, CH₂), 4.10 (3H, s, Me), 2.66 (4H, s, CH₂); δ_C (100 MHz; CDCl₃) 181.7, 176.4, 171.4, 133.8, 133.6, 133.3 (CH), 132.7 (CH), 131.2, 126.43 (CH), 126.36 (CH), 125.5, 118.0, 69.5 (CH₂), 37.0 (Me), 25.5 (CH₂); HPLC: purity (AUC) 98.4%.

1-Methyl-3-(4-methylsulfonylphenoxy)methyl-1H-benz[f]indole-4,9-dione 25

Prepared by general procedure 3 from 3-hydroxymethyl-1-methyl-1H-benz[f]indole-4,9-dione 29i (50.0 mg, 0.207 mmol) and 4-methylsulfonylphenol (250 mg, 1.45 mmol). Column chromatography eluting with ethyl acetate-dichloromethane (1:9) gave the title compound as a yellow solid (58.0 mg, 71%); mp 210–212 °C; (Found: M+Na⁺, 418.0719. C₂₁H₁₇NO₅SNa requires 418.0720); λ_max (acetonitrile)/nm 246 (log ε 4.47), 278 (4.09), 326 (3.64), 388 (3.43); ν_max (CHCl₃)/cm⁻¹ 3012, 1657, 1595, 1319, 1257, 1147; δ_H (400 MHz; CDCl₃) 8.19-8.13 (2H, m, H-5, H-8), 7.91-7.87 (2H, m, H-6, H-7), 7.73-7.69 (2H, m, ArH), 7.16-7.13 (2H, m, ArH), 7.02 (1 H, s, H-2), 5.49 (2H, s, CH₂), 4.09 (3H, s, NMe), 3.05 (3H, s, SO₂Me); δ_C (100 MHz; CDCl₃) 181.7, 176.3, 162.6, 133.8, 133.7, 133.28 (CH), 133.26 (CH), 132.6, 131.1, 130.1 (CH), 129.6 (CH), 126.5 (CH), 126.4 (CH), 124.6, 120.4, 115.2 (CH), 63.2 (CH₂), 44.8 (Me), 36.9 (Me); HPLC: purity (AUC) 98.2%.

Cancer growth inhibition assay

All human cancer cell lines were obtained from ATCC. The ability of indolequinones to induce growth inhibition in human cancer cell lines was measured using the MTT assay as previously described.^16,17

Scheme 3.

Functionalization of 3-hydroxymethylindolequinones. R¹, R⁵, R⁶ and Y defined in Table 1.