Nucleophilic alkenes. IX. Addition of 1,1-dimethoxyethene to azanaphthoquinones: synthesis of bostrycoidin and 8-O-methylbostrycoidin

Abstract

Reaction of 1,1-dimethoxyethene with azanaphthoquinones leads to pairs of isomeric dimethoxy-azaanthraquinones by means of 1:2-addition. A photochemical procedure has been developed for substituting these dimethoxy products by a further methoxy, amino or a hydroxy group peri to carbonyl. In this way the antibiotic bostrycoidin (1) and its 8-O-methyl derivative (2), the only natural 2-azaanthraquinones, have been synthesized for the first time.