Synthesis and alpha 1-adrenoceptor antagonistic activity of some 4-amino-5,7-dimethyl-2-(substituted) aminopyrido (2,3-d) pyrimidines.

A series of new 4-amino-5,7-dimethyl-2- (substituted)aminopyrido(2,3-d)pyrimidines (5) have been synthesized and tested for selective alpha 1-adrenoreceptor antagonistic activity. Some of the compounds were found to antagonize alpha 1-adrenoreceptor in a competitive and reversible manner. When screened on rat anococcygeus muscle some of the compounds exhibited significant alpha 1-adrenoreceptor antagonistic activity (pA2 values in the range of 5.