Synthesis and structure activity relationship of substituted thiazoles

Differently substituted thiazoles viz 1,3-benzothiazol-2-amines (1–3), 4-arylthiazol-2-amines (4–6), 3-(benzo[d] thiazol-2-yl)-2-phenylthiazolidin-4-ones (1a-3a) and 2-phenyl-3-(4-phenylthiazol-2-yl)thiazolidin-4-ones (4a-6a) were synthesized and assayed for their antifungal activity against the phytopathogenic fungus Drechslera oryzae causing brown leaf spot of rice. Most of the hybrid thiazoles revealed strong activity against the test fungus. Thiazol-2-amines displayed better inhibition of colony growth of D. oryzae than thiazol-2-ylthiazolidin-4-ones. Compound 1 showed maximum fungitoxicity (ED₅₀=42 μg/ml) comparable to the standard fungicide Tilt (propiconazole) against D. oryzae. Structure activity relationship of fungitoxicity with drug like molecular descriptors viz. Mv, TPSA and Log p was explained.