Studies on 1, 2, 3, 4-Tetrahydroisoquinoline Derivatives. I. Syntheses and β-Adrenoceptor Activities of Positional Isomers of Trimetoquinol with Respect to Its 6, 7-Dihydroxyl Groups

Abstract

In a series of phenylethanolamine β-stimulants, transformation of hydroxyl groups of the catechol type into those of the resorcinol type has been reported to improve the bioavailability. Therefore, five possible positional isomers (1-5) of trimetoquinol (TMQ) with respect to its 6, 7-dihydroxyl groups were synthesized and tested for bronchodilating activity. Among these positional isomers, the 5, 7-dihydroxyl derivative (4) exhibited more potent bronchodilating activity and longer duration of activity than (±)-TMQ and isoproterenol on intraduodenal administration.