(-)-β-Narcotine: A facile synthesis and the degradation with ethyl chloroformate

Abstract

(-)-β-Narcotine (6), a phthalideisoquinoline alkaloid, was synthesized conveniently by the direct condensation of cotarnine (1) and iodomeconine (2) prepared by aromatic iodination using thallium trifluoroacetate/KI and by the successive reduction of resulting iodo-β-narcotine (5) with aluminum amalgam. Its structure including a stereochemistry was confirmed by instrumental analyses. This synthetic alkaloid was degraded with ethyl chloroformate at room temperature to afford the chloro-carbamate 6b as a crystalline intermediate, which was unexpectedly converted into the carbinol 8 by exchange of Cl with OH of water contained in the solvents and the ethoxy-carbamate 9, probably because of ethanol added to chloroform as a solvent stabilizer during the purification by column chromatography.