Synthesis and antihypertensive activity of some imidazoindole derivatives

Abstract
The synthesis of pyridino[1,2-.alpha.]imidazo[5,4-.beta.]indole (1) and thiazolo[3,2-.alpha.]imidazo[5,4-.beta.]indole (2) was achieved by phosphite reduction of 3-nitroso-6-phenylimidazo[1,2-.alpha.]pyridine and 5-nitroso-6-phenylimidazo[2,1-.beta.]thiazole. Compound 1 has shown strong antihypertensive activity in spontaneously hypertensive rats while compound 2 showed similar bioactivity in spontaneously hypertensive rats and in normotensive dogs. A tricyclic amino derivative, 3-amino-2-phenylimidazo[1,2-.alpha.]pyridine, which has structural resemblance to compound 1, showed no hypotensive activity.