Synthesis and identification of the major metabolites of prazosin formed in dog and rat

Article abstract of DOI:10.1021/jm00211a031

The 6 O demethyl and 7 O demethyl analogues of the new antihypertensive drug prazosin [2 [4 (2 furoyl) piperazin 1 yl] 4 amino 6,7 dimethoxyquinazoline hydrochloride] have been unequivocally synthesized via separate ten step reaction sequences starting from isovanillin and vanillin, respectively. The 6 O demethyl derivative was found to be identical with the major prazosin metabolite formed in dog and rat, while the 7 O demethyl derivative was identical with another, less prevalent but significant metabolite. Two minor metabolites of prazosin, 2 (1 piperazinyl) 4 amino 6,7 dimethoxyquinazoline and 2,4 diamino 6,7 dimethoxyquinazoline, are also described. All four metabolites are less potent blood pressure lowering agents in dogs than prazosin but may contribute to its antihypertensive effect, since they account for a major portion of the administered dose.