Syntheses of 3-O-Demethylthalicthuberine and N-Acetyl-seco-N-methyllaurotetanine

Abstract

The structures previously assigned to the phenanthrene alkaloids 3-O-demethylthalicthuberine and N-acetyl-seco-N methyllaurotetanine have been confirmed by total syntheses in which the key step involved formation of ring C of the aporphine alkaloids (±)-isodomesticine and O-benzyl-N-methyllaurotetanine by a radical-initiated cyclization. Opening of ring B of (±) isodomesticine with methyl chloroformate and subsequent reduction of the N-carbomethoxy group afforded 3-O demethylthalicthuberine. Similarly, ring-B opening of N-methyllaurotetanine with acetyl bromide followed by hydrolysis afforded N-acetyl-seco-Nmethyllaurotetanine.

Keywords

• alkaloid
• aporphine
• phenanthrene
• synthesis
• radical cyclization