An alternative total synthesis of N-methylcaaverine through phenolic oxidation

Abstract

Phenolic oxidation of 1,2,3,4-tetrahydro-7-hydroxy-1-(2-hydroxybenzyl)-6-methoxy-2-methylisoquinoline (Ib) afforded the dienone (IIb) in 2·4% yield, the dimeric benzylisoquinoline (XIa) in 1·1% yield, and an unknown carbonyl compound. Borohydride reduction of the dienone (IIb) gave the corresponding dienol(XVII), whose rearrangement in acidic media gave the 1-hydroxy-2-methoxyaporphine (XVIII). This aporphine was identical with (±)-N-methylcaaverine (XVIII), which was derived from the (±)-caaverine (XIX) by Eschweiler–Clarke reaction.