Abstract: There are disclosed a 4-aminophenol derivative of the formula: ##STR1## (wherein R.sup.1 and R.sup.2 each represent a lower alkyl group, Y represents a single bonding arm, a lower alkylene group or a lower alkenylene group, R.sup.3 represents a thienyl group or pyrrolyl group which may be also substituted with a lower alkyl group; benzothienyl group, indolyl group; or a phenol group which is substituted with 1 to 2 groups selected from a lower alkoxy group and a lower alkanoyloxy group; or Y-R.sup.3 represents integrally an alkyl group with 6 to 9 carbon atoms; or a hydrocarbon group with 5 to 14 carbon atoms having 2 or 3 double bonds) or a pharmacologically acceptable salt thereof, and processes for preparing the same.

Abstract: A compound of the formula: ##STR1## wherein R.sup.1 is hydrogen or methyl, is prepared by condensing a compound of the formula: ##STR2## wherein R.sup.2 is alkyl, aryl or aralkyl and R.sup.1 is same as above, or a reactive derivative thereof with 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid or an ester thereof to give a compound of the formula: ##STR3## wherein R.sup.3 is an ester residue and R.sup.1 and R.sup.2 are same as above, followed by hydrolysis or ammonolysis of said compound (IV). The compound (I) is useful as a diagnostic or therapeutic agent for angiotensin-related hypertension.