Synthesis and .beta.-adrenoceptor activity of the erythro and threo isomers of substituted .alpha.-hydroxytrimetoquinol

Abstract
The synthesis and pharmacological activity of erythro- and threo-isomers of 1-(3'',4'',5''-trimethoxy-.alpha.-hydroxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, were reported. Structural assignments were based upon NMR spectra of the 6,7-dibenzyl precursors and of the synthetic derivatives of 13.alpha.- and 13.beta.-hydroxy-2,3-(dibenzyloxy)-9,10,11-trimethoxytetrahydroprotoberberine respectively. The erythro-isomer was a more potent .beta.-adrenoceptor stimulant than the threo-isomer in guinea pig atrial, guinea pig tracheal, and rat adipocyte preparations. The differential activity of these compounds on lipolysis was favorably correlated to changes in the stimulation of adenylate cyclase activity and c[cyclic]AMP accumulation in rat adipocytes.