A total synthesis of (±)-capaurimine

Abstract

Capaurimine (2) was synthesised by a Mannich reaction of 8-benzyloxy-1-(4-benzyloxy-3-hydroxybenzyl)-1,2,3,4-tetrahydro-6,7-dimethoxyisoquinoline (16), followed by methylation of the Mannich base (6) and debenzylation of the resulting compound (9). The intramolecular Mannich reaction occurred preferentially at the position ortho to the hydroxy-group.

The isolation of (±)-capaurimine together with (±)-kikemanine (4) and (±)-tetrahydropalmatine (5) from a quaternary basic fraction of Corydalis pallida var. tenuis(Yatabe) is also described.