Studies on the syntheses of heterocyclic compounds. Part 679. A stereoselective total synthesis of (±)-ophiocarpine; a simple route to 13-hydroxyberbines

Abstract

Phenolic cyclisation of (1R*)-1-[(α,R*)-α,3-dihydroxy-4-methoxybenzyl]-1,2,3,4-tetrahydro-6,7-methylenedioxy-isoquinoline (21) gave 10-methoxy-2,3-methylenedioxy-13aα-berbine-9,13β-diol (33) and the isomeric 11,13β-diol (34). 9-O-Methylation of the diol (33) gave (±)-ophiocarpine (3). A general synthesis of 13-hydroxy-berbines from 1,2,3,4-tetrahydro-α-hydroxybenzylisoquinolines by Mannich reaction and phenolic cyclisation is described.