The synthesis of N-phenoxyethyl-1-substituted-1,2,3,4-tetrahydroisoquinolines and their alpha1-adrenoceptor blocking activity.

A series of phenoxyisoquinolines, N-phenoxyethyl-1-(2-nitrophenyl)-1,2,3,4-THIQs 3a-3d, N-phenoxyethyl-1-benzyl-1,2,3,4-THIQ 3e, N-phenoxyethyl-1-(2-aminophenyl)-1,2,3,4-THIQs 5f-5i, N-phenoxyethyl-1-(2-phenoxyethylaminophenyl)-1,2,3,4-THIQs 5f'-5i', have been synthesized and tested in isolated rat vas deferens alpha-adrenoreceptors. Comparison of pA2 values for these compounds in the presence of phenylephrine confirms that alpha(1)-adrenoceptor blocking activity of 3a-3d (-NO(2) series) is more active than 6a-6c (-NH(2) series) in the aortic rings isolated from SD rats. On the other hand, the electron-donating group at the 6-position of isoquinoline ring either increases or decreases the alpha(1)-adrenoceptor blocking activity.