Abstract: The synthesis of 11 novel compounds of 5-substituted 2-amino-l,3,4-thiadiazole and 2-substituted amino-l,3,4-thiadiazoles are described.The bactericidal activity against Xanthomonas campestris pv oryzae in vivo of about 30 ATDA analogues is observed.2-Amino-5-car-boxyl-l,3,4-thiadiazole exhibites an excellent bactericidal activity.It is postulated that the acive compound which can serve as the competitor of nicotinamide in metabolite.system in bacteria cell seems to be 2-amino-5-carboxyl-l,3,4-thiadiazole rather than ATDA itself.

Key words: 2-Amino-1,3,4-thiadiazole compounds, Antibacterial activity, Leaf, blight of rice Synthesis, Structure-property relation