Studies on quinones. Part 34: The reaction of styrene with activated 1,4-benzoquinones: access to potential antiprotozoal pyranobenzoquinones

Access to New Cytotoxic Quinone-Amino Acid Conjugates Linked through A Vinylic Spacer from 2-Acylnaphthoquinones and Methyl 3-Aminocrotonate

The reaction of 2-acetyl- and 2-benzoyl-1,4-naphthoquinone with (Z)-methyl 3-(hydroxymethyl)aminocrotonate proceeds through a formal [3+3] process to yield the corresponding 1,2-dihydrobenzisoquinolinequinones in 63% and 72% yield, respectively. The reactions of 2-acyl-1,4-naphthoquinone with enaminones, derived from diverse l- and d-amino acid methyl esters, produced the corresponding naphthoquinone amino acids conjugates bonded through a vinyl spacer in the yields range 40–71%. The presence of not-separable isomers of the naphthoquinone amino acids conjugates in the ¹H- and ¹³C-NMR spectra is explained by the existence of conformational isomers generated by hindered rotation of the substituent bonded to the quinone double bond. These new naphthoquinone amino acids conjugates were screened in vitro on normal and cancer cell lines and showed moderate cytotoxic activities.

Synthetic approaches and in vitro cytotoxic evaluation of 2-acyl-3-(3,4,5-trimethoxyanilino)-1,4-naphthoquinones

2-Acyl-1,4-naphthoquinones react with 3,4,5-trimethoxyaniline, under aerobic conditions, to give benzophenanthridinequinone, benzocarbazole and 2-acyl-3-(3,4,5-trimethoxyanilino)-1,4-naphthoquinone derivatives.

Eco-friendly synthesis and antiproliferative evaluation of some oxygen substituted diaryl ketones

A broad variety of oxygen-substituted diaryl ketones has been synthesized by solar energy-induced Friedel Crafts acylations of 1,4-benzo- and 1,4-naphthoquinones with benzaldehydes. The in vitro antiproliferative properties of the photoproducts were assessed on prostate (DU-145), bladder (T24) and breast (MCF7) human-derived tumor cell lines and compared to non-tumor mouse fibroblasts (Balb/3T3). Among the tested compounds, it was found that those containing a 3,4,5-trimethoxyphenyl A-ring, such as 12 and 22 are more active on DU-145, with EC₅₀ values of 1.2 and 5.9 μM, respectively. By comparing their effects on the three cancer cell lines, the analogue 22 has the best mean selective index (2.4).

Studies on quinones. Part 39: Synthesis and leishmanicidal activity of acylchloroquinones and hydroquinones

Acylhydroquinone-based compounds are attractive targets for the design of new leishmanicidal drugs. We have previously described sesquiterpene quinones and hydroquinones series, which exhibit different degree of potency against Leishmania amazonensis. The present study details the preparation of acylchloroquinones and hydroquinones possessing lipophilic substituents and examines their in vitro activity against intracellular L. amazonensis amastigotes. The quinone or hydroquinone nucleus is essential for the activity of the members of the series. The lipophilicity of the cycloaliphatic systems in these members seems to attenuate the cytotoxical effect and increases the selectivity of those compounds containing the norbornene system.

Preparation of 1,4-hydrobenzoquinones by the PCC/SiO2-promoted double oxidation of 3-cyclohexene-1,2-diols

The PCC/SiO2-promoted double oxidation of 3-cyclohexene-1,2-diols, which were easily prepared by the two-step sequence of alpha'-hydroxylation of various conjugated cyclohexenones and the subsequent nucleophilic carbonyl addition of alkyl anions, produced diversely substituted 1,4-hydrobenzoquinones.

Studies on quinones. Part 37. Synthesis and biological activity of o-aminoester functionalised benzo- and naphtho[2,3-b]thiophenequinones

The synthesis of 3-amino-2-methoxycarbonyl-4,7-dimethoxybenzo[b]thiophene (5) and benzothieno[3,2-d][1,3]oxazin 15 from 3,6-dimethoxy-2-nitrobenzaldehyde (1) is reported. Benzo[b]thiophene-4,7-quinones 9 and 10 were prepared in good yields by oxidative deprotection of the corresponding dimethoxybenzothiophenes 8 and 7. Cycloaddition reaction of quinone 8 with 1-(E)-trimethylsilyloxy-1,3-butadiene followed by acid-induced aromatization provides access to naphtho[2,3-b]thiophene-4,9-quinone 13 and 14. The in vitro activity of the new quinones against Leishmania amazonensis and human-T-cell leukemia virus type 1 (HTLV-1) is reported.