Reaction of protoberberine-type alkaloids. Part 13. Biogenetic conversion of protoberberine alkaloids into phthalideisoquinoline alkaloids

Abstract

A new convenient and biogenetic-type conversion of the protoberberine alkaloids into the phthalideisoquinoline alkaloids is described. The phthalideisoquinoline 5,6-dimethoxy-3-(6,7-dimethoxyisoquinolin-1-yl)isobenzofuran-1(3H)-one (4) was derived from 8-norcoralyne chloride (1)via 13-oxidonorcoralyne (3) in a one-pot reaction consisting of dye-sensitized photo-oxygenation followed by treatment with sodium borohydride. The conversion of berberine chloride into (±)-β-hydrastine (21) was performed by a reaction sequence involving conversion of 8,13a-epidioxy-9,10-dimethoxy-2,3-methylenedioxy-13-oxo-5,6,13,13a-tetrahydro-8H-dibenzo[a,g]quinolizine (9) into 1-(2-carboxy-3,4-dimethoxybenzoyl)-3,4-dihydro-6,7-(methylenedioxy)isoquinoline (11) using pyridinium chloride, followed by methylation and reductive cyclization.