Synthesis and biological activity of pyrazolopyrimidines

A series of 1-(4-substituted phenyl/benzoyl)-5-(4-substituted phenyl) pyrazolo(3,4-d) pyrimidin-4-oxo-6-thiones (19-33) were synthesized by the cyclization of ethyl 1-(4-substituted phenyl/-benzoyl)-5-(4-substituted phenyl) thioureidopyrazole-4-carboxylates (4-18). Condensation of 19-33 with chloroacetic acid in alcoholic sodium hydroxide furnish ed 1-(4-substituted phenyl/benzoyl)-5-(4-substituted phenyl) pyrazolo (4,3-d) pyrimidin-4-oxo-6-thioacetic acids (34-48), which on reduction with sodium borohydride, followed by cyclization using acetic anhydride and pyridine afforded 5H-thiazolido (3,2-a)-8-(4-substituted phenyl/benzoyl)-pyrazolo(4,3-e)-4-(4-substituted phenyl)pyrimidyl-1,5-diones (49-63). All the compounds were screened for their antimicrobial activity against Staphylococcus aureus, Escherichia coli and Candida albicans. Compound 51 showed most significant antifungal activity (zone of inhibition, 34 mm). None of the compounds have shown any significant antibacterial activity.