8-(4'-Thiazolyl) purines and deazapurines were obtained by condensation of 4- carboxythiazole derivatives with 4, 5-diaminopyrimidines or pyridines. Thus, the 8-(4'- thiazolyl) derivatives of purine (2), adenine (4), hypoxanthine (6), guanine (12), 6-mercapto- (8) and 6-methylmercaptopurine (lo), and others were obtained. Chlorination of 10 led to the 6-methylsulfonyl compound 23, which upon reaction with hydrazine gave 8-(4'-thiazolyl)-6 ...