Synthesis of Protoberberine Derivatives as Hypotensives. IV. Synthesis of 11-O-Demethylxylopinine (11-hydroxy-5, 6, 13, 13a-tetrahydro-2, 3, 10-trimethoxy-8H-dibenzo [a, g] quinolizine) and Its Acyl Derivatives, and Optical Resolution of (±)-Xylopinine (Studies on the Syntheses of Heterocyclic Compounds. DXXXI

Abstract

When O-demethylxylopinine (XIII) was synthesized from 1-(3-hydroxy-4-methoxybenzyl)-6, 7-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline (XI), 11-hydroxy-9-hydroxymethyl-2, 3, 10-trimethoxy-5, 6, 13, 13a-tetrahydro-8H-dibenzo [a, g] quinolizine (XIV) was also formed. Accordingly, in order to prevent formation of this by-product, 11-benzyloxy-2, 3, 10-trimethoxy-5, 6, 13, 13a-tetrahydro-8H-dibenzo [a, g] quinolizine (XII), which was synthesized by the Eschweiler-Clarke reaction of 1-(3-benzyloxy-4-methoxybenzyl)-6, 7-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline (X), was debenzylated to give XIII in a good yield. On the other hand, several 11-acyloxyprotoberberine derivatives. (XVIIa-f), which were expected as hypotensives, were synthesized by acylation of XIII with acetic anhydride and acid chloride. Optical resolution of (±)-xylopinine was carried out from which optically active xylopinine was obtained.