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2-[6-(Morpholin-4-yl)pyridin-3-ylamino]acetohydrazide (4) was obtained starting from 6-morpholin-4-ylpyridin-3-amine (2) via the formation of ester (3) and then converted to the corresponding Schiff bases (5, 6) with the reaction with aromatic aldehydes. The carbothioamide (9), obtained from the reaction of hydrazide with phenylisothiocyanate, was converted to the corresponding 1,2,4-triazole (11) and 1,3,4-thiadiazole (12) derivatives by the treatment with NaOH or H2SO4, respectively. The cyclocondenzation of 9 with 4-chlorophenacyl bromide or ethyl bromoacetate produced the corresponding 1,3-thiazole (10) or 1,3-thiazolidine derivatives (13), respectively. Antimicrobial and antiurease activities of newly synthesized compounds were investigated. Some of them were found to be active on M. smegmatis, and they displayed activity toward C. albicans and S. cerevisiae in high concentration. Compound 10 proved to be the most potent showing an enzyme inhibition activity with an IC50 = 2.37 ± 0.19 μM.

4-Aryl-5-(pyridin-3-yl)-4H-1,2,4-triazole-3-(thi)oles 5-7, obtained starting from nicotinic acid hydrazide were converted to the corresponding Mannich bases 12-24 by the reaction with several heterocyclic amines in the presence of formaldehyde. The synthesis of S-alkylated compounds 8-11 was performed from the reaction of the corresponding triazol-5-thioles with various alkyl halides. The condensation of carbo(thio)amides 2-4 with 4-chlorophenacyl bromide afforded the corresponding 1,3-thia(oxa)zol-2(3H)-ylidene]pyridine-3-carbohydrazides 25-27. 1,3-Thia(oxa)zolidine derivatives 28-30 were obtained from the cyclization reaction between compounds 2-4 and ethyl bromoacetate. All newly synthesized compounds were screened for their antimicrobial, antiurease, and antilipase activities. The biological activity studies revealed that all the compounds screened showed good or moderate antimicrobial, antiurease, and/or antilipase activity.

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