A series of new 3,4,5-substituted 1,2,4-triazoles were synthesized. Their SH-alkylation by various alkylating compounds and aminomethylation leading to the formation of Mannich bases were studied. The influence of the synthesized compounds on the level of DNA methylation and their antitumor and antibacterial properties were investigated. Several compounds with pronounced demethylation and weak antitumor and antibacterial activities were identified. Correlations among the investigated biological properties were not found.In continuation of research on the search for biologically active 1,2,4-triazole derivatives [1 -5], herein the synthesis and several transformations of new 3,4,5-substituted 1,2,4-triazoles with a 4-chlorophenoxymethyl group in the heterocycle 3-position, in contrast with the previous compounds, were reported. The previously synthesized analogs with a 4-bromophenyl or 4-bromophenoxymethylene substituent in this position exhibited moderate experimental antitumor activity [4]. It seemed interesting to study the effect of the new triazole derivatives on the level of tumor DNA methylation and to find a possible correlation between the ability to inhibit DNA methylation and the antitumor activity. The series of synthesized compounds were also tested for antibacterial activity based on published reports of the antibacterial properties of 1,2,4-triazole derivatives [6,7].Scheme 1 illustrates the syntheses of the 1,2,4-triazoles.The starting compounds were 1,4-substituted thiosemicarbazides that were prepared by reacting 4-chlorophenoxyacetic acid hydrazide with allyl-, phenyl-, benzyl-, 3-bromo-4-methoxybenzyl-, and cyclohexylisothiocyanates in EtOH [3,4]. Alkaline cyclization of thiosemicarbazides I yielded 3,4-substituted 5-thio-1,2,4-triazoles II -VI, which were stable crystalline compounds. Halides of certain structures, i.e., aliphatic and unsaturated acid chlorides or bromides or their esters and amides, were selected for alkylation of the 5-thio group of triazoles II -VI. The alkylation was performed using the methods developed previously by us, i.e., refluxing the triazoles with the appropriate halides in EtOH or H 2 O in the presence of a certain amount of KOH [4]. As a result, a series of new 3,4,5-substituted triazoles (VII -XXV) were synthesized as colorless crystalline compounds.Aminomethylation of triazoles II -VI to give the corresponding Mannich bases was carried out in MeOH with an excess of secondary amine and formalin at room (20 -25°C) temperature. The obtained 1-N-morpholinomethylene-1,2,4-triazolinethiones-5 (XXVI -XXX) were slightly yellowish stable crystalline compounds. Only starting triazole IV was isolated after an attempt to synthesize the corresponding thiazolino-1,2,4-triazole via bromination in CHCl 3 of 4-allyl-5-thio-1,2,4-triazole (IV) by the literature method [8]. The intended reaction product was obtained via bromination of IV in anhydrous EtOH at room temperature followed by refluxing for 4 h.
