Studies in protoberberine alkaloids. Part II. Structures of isooxyberberine and isooxyepiberberine

Abstract

Isooxyberberine reported to be formed by hot acid treatment of oxyberberine (I) is shown to have structure V arising from I by selective cleavage of one methoxyl group. Structure IV assigned previously to isooxyepiberberine, obtained from oxyepiberberine (III), has been corrected to VII; the conversion of l,2-dihydro-2-methyl-7,8-methylenedioxy-l-oxo-isoquinoline (VIII), with part structure of III, to the corresponding 7,8-dihydroxy compound (IX) under acid conditions has been used as a model for assignment of structure VII.