A series of novel ([1,2,4]triazolo[1,5-c]quinazolin-2-ylthio)carboxylic acids 2a—d and esters 3a—l were synthesized and evaluated for antimicrobial activity. Alkylation of potassium 2-thio-[1,2,4]triazolo[1,5-c]quinazoline 1 with halogenocarboxylic acids and its esters proceeded S-regioselectively. During acid catalyzed esterification of 2a—c, degradation of the pyrimidine ring was observed. The structures of the compounds were elucidated by FT-IR, 1H- and 13C-NMR, electron impact mass spectra (EI-MS) and LC-MS spectral data. Antimicrobial and antifungal activity of synthesized compounds was tested against Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, Mycobacterium luteum, Candida albicans and Candida tenuis. Acids 2a and 2c exhibited significant activity against C. albicans, which was additionally confirmed by the bioluminescence inhibition test and interrelated with their lipophilicity.

The combinatorial library of novel potential anticancer agents, namely, 2-(alkyl-, alkaryl-, aryl-, hetaryl-)[1,2,4]triazolo[1,5-c]quinazolines, was synthesized by the heterocyclization of the alkyl-, alkaryl-, aryl-, hetarylcarboxylic acid (3H-quinazoline-4-ylidene)hydrazides by oxidative heterocyclization of the 4-(arylidenehydrazino)quinazolines using bromine, and by the heterocyclization of N-(2-cyanophenyl)formimidic acid ethyl ester. The optimal method for synthesis of the s-triazolo[1,5-c]quinazolines appeared to be cyclocondensation of the corresponding carboxylic acid (3H-quinazoline-4-ylidene)hydrazides. The compounds' structures were established by (1)H, (13)C NMR, LC- and EI-MS analysis. The in vitro screening of anticancer activity determined the most active compound to be 3,4,5-trimethoxy-N'-[quinazolin-4(3H)-ylidene]benzohydrazide (3.20) in micromolar concentrations with the GI50 level (MG_MID, GI50 is 2.29). Thus, the cancer cell lines whose growth is greatly inhibited by compound 3.20 are: non-small cell lung cancer (NCI-H522, GI50=0.34), CNS (SF-295, GI50=0.95), ovarian (OVCAR-3, GI50=0.33), prostate (PC-3, GI50=0.56), and breast cancer (MCF7, GI50=0.52), leukemia (K-562, GI50=0.41; SR, GI50=0.29), and melanoma (MDA-MB-435, GI50=0.31; SK-MEL-5, GI50=0.74; UACC-62, GI50=0.32). SAR-analysis is also discussed.

Potassium 8-R(1)-9-R(2)-10-R(3)-3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazoline-6-thiolates 2.1-2.26 were synthesized via cyclocondensation of 6-R-3-(3-R(1)-4-R(2)-5-R(3)-aminophenyl)-1,2,4-triazin-5-ones 1.1-1.26 with carbon disulfide, potassium hydroxide, and ethanol or with potassium O-ethyl dithiocarbonate in 2-propanol. The corresponding thiones 3.1-3.26 were obtained by treatment of 2.1-2.26 with hydrochloric acid. It was found that the nature of the substituents in positions 3, 4, and 5 of the corresponding 6-R-3-(3-R(1)-4-R(2)-5-R(3)-aminophenyl)-1,2,4-triazin-5-ones were affected on the terms of the reaction. The structures of compounds were proven by a complex of physicochemical methods ((1)H, (13)C NMR, LC-MS, and EI-MS). The results of the antibacterial and antifungal activity assay allowed the determination of the high sensitivity of Staphylococcus aureus ATCC 25923 (MIC 6.25-100 μg/mL, MBC 12.5-200 μg/mL) to the synthesized compounds.