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

One-Pot Synthesis of 2-R-Naphtho[2,3-b]thiophene-4,9-diones via Cyclization of 2-(R-Ethynyl)-1,4-naphthoquinones with Na2S2O3

The concise and efficient one-pot synthesis of 2-R-naphtho[2,3-b]thiophene-4,9-diones from 2-bromo-1,4-naphthoquinone and alkynes has been developed. The reaction proceeds through the formation of 2-(R-ethynyl)-1,4-naphthoquinones, which undergo transformation with Na₂S₂O₃ to 2-R-naphtho[2,3-b]thiophene-4,9-diones via C-H sulfuration, accompanied by the formation of the aromatic Bunte salt, followed by its air oxidation and 5-endo-dig cyclization. The protocol is characterized by simplicity, good tolerance for functional groups, relatively mild conditions, and commercially available starting compounds.

A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones

A new and efficient method for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones in one step with high yields from the reaction of lawsone with 1,3,5-triazinanes was developed.

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.

Synthesis and antifungal activity of 5-arylamino-4,7-dioxobenzo[b]thiophenes

5-Arylamino-4,7-dioxobenzo[b]thiophenes 3-6 were synthesized and tested for in vitro antifungal activity against Candida and Aspergillus species. 5-Arylamino-6-chloro-2-(methoxycarbonyl)-4,7-dioxobenzo[b]thiophenes 5 showed, in general, more potent antifungal activity against Candida species than the other 4,7-dioxobenzo[b]thiophenes 3, 4 and 6. The results suggest that 5-arylamino-4,7-dioxobenzo[b]thiophenes would be potent antifungal agents.

Studies on Quinones. Part 38: synthesis and leishmanicidal activity of sesquiterpene 1,4-Quinones

The reaction of (+)-euryfuran 1 with several benzo-, naphtho- and benzo[b]thiophene-1,4-quinones in acetic acid yields the corresponding euryfuryl-1,4-quinones 3, 5, 7, 8, 10, 12, and 14. The structure of compounds 7, 8, 12, and 14 was assigned through 2D NMR 1H-13C HMBC experiments. The influence of the acidity of the solvent upon the reactivity and regioselectivity of the quinones to the oxidative coupling reaction, is discussed. The in vitro activity of the euryfurylquinones and their corresponding precursors against Leishmania amazonensis is described.

Synthesis and antiprotozoal activity of naphthofuranquinones and naphthothiophenequinones containing a fused thiazole ring

The synthesis of tetracyclic quinones 10a,b, 14a,b, 19a,b and 20a,b is described. The preparations involve regioselective Diels-Alder reactions via trapping the thiazole o-quinodimethane 9 with several benzofuranquinones and benzothiophenequinones. The structure of the regioisomers was assigned through 2D NMR 1H-13C HMBC experiments performed on 10a and 14a. Compounds 10a,b, 14a as well as phenol 1 and the starting quinones 2, 5, 7 and 15 are evaluated against Leishmania sp., Toxoplasma gondii and THP-1 cells. Almost all the tested compounds exhibit significant antiprotozoal activities with lower cytotoxicities than the reference compounds. Among them, quinones 2 and 14a possess the best activities towards L. donovani and T. gondii with the lowest toxicities.