Buxus alkaloids. Part VIII. The isolation and constitution of a new alkaloid, cyclokoreanine-B, from B. koreana Nakai, and the conversion of cyclomikuranine into cyclovirobuxine-A

Abstract

An investigation of the alkaloidal constituents of Buxus koreana Nakai led to the isolation of a new alkaloid, cyclokoreanine-B, besides seven known alkaloids. Although all of the hitherto identified Buxus alkaloids bearing an amino-substituent at C(3) possess the β-configuration at that centre, this alkaloid is assumed to have an α-oriented 3-dimethylamino-group. The inter-relation of cyclomikuranine (X), isolated from the weak base fraction of Buxus microphylla Sieb. et Zucc. var. suffruticosa Makino forma major Makino, with cyclovirobuxine-A (XII). derived from cyclomicrophylline-A (XIVb). was achieved by conversion of the former into the oxime (XI) and subsequent reduction with lithium aluminium hydride to the primary amine, followed by N-methylation.