Studies in protoberberine alkaloids: Part IV. Synthesis of 13-Methyl-Ψ-coptisine

Abstract

Tetrahydro-13-methyl-y-coptisines (V) (m.p. 195°) and (VI) (m.p. 131°) have been synthesized from l-(α-methyl-3,4-methylenedioxybenzyl)-l,2,3,4-tetrahydro-6,7-methylenedioxyiso-quinoline (IV) by treating it with formaldehyde and hydrochloric acid. The products obtained as a mixture have been separated by column chromatography over silica using chloroform for eluting the column. Mercuric acetate oxidation of V-afforded 13-methyl-Ψ-coptisine (VII). Comparison of the melting points of the iodides and chlorides of VII and worenine suggests that worenine may be 13-methyl-Ψ-coptisine.