Racemisation. Part I. Racemisation of protoberberines under the conditions of catalytic hydrogenation

Abstract

Treatment of optically active protoberberine alkaloids, namely (–)-coreximine (II), (–)-tetrahydropalmatine (III), and (–)-norcoralydine (IV), with hydrogen in the presence of platinum oxide afforded the corresponding racemic protoberberines. Catalytic hydrogenolysis of (–)-[13,13,13a-D₃]coreximine (VI) and (-)-[13,13,13a-D₃]norcoralydine (VIII) gave racemised products with the expected mass spectra.