SYNTHESIS OF 1,3,4-THIADIAZOLE AND 1,2,4-TRIAZOLE ACYCLO C-NUCLEOSIDES

Reaction of 4-arylthiosemicarbazides (1) with 2,3,4,5-tetra-O-acetylga lactaroyl dichloride(2) gave the corresponding -O-acetylgalactaroyl-bi s-4-aryl-thiosemicarbazides (3). The latter compounds underwent dehydr ative cyclization by heating with phosphoryl chloride to give -arylami no-1,3,4-thiadiazol-2-yl)galacto-tetritols (4) which afforded, upon de -O-acetylation with methanolic ammonia, the corresponding -arylamino-1 ,3,4-thiadiazol-2-yl)galacto-tetritols (5). Compounds 3 were also cycl odehydrated, in a different way, with concomitant de-O-acetylation upo n treatment with ethanolic sodium ethoxide to give aryl-5-thioxo-1,2,4 -triazol-3-yl)galacto-tetritols (6). Acetylation of 6 with acetic anhy dride in the presence of pyridine afforded aryl-5-thioxo-1,2,4-triazol -3-yl)galacto-tetritols (7). Compounds 3a, 3b and 6a-c showed no antib acterial activity against Bacillus subtilis, Escherichia coil, Pseudom onas aeruginosa, or Staphylococcus aureus and showed weak to moderate antifungal activity against Aspergillus terreus and Candida albicans.