Structure of a Derivative of Cryptopleurine

Abstract

CRYPTOPLEURINE is an alkaloid isolated in 1948 by de la Lande¹ from Cryptocarya pleurosperma. It has a very high toxicity approaching that of strychnine, possesses marked vesicant properties of the same order as the nitrogen mustards¹, is a mitotic poison^2,3 and, in small concentrations, stimulates nerve regeneration⁴. Due to the interest in its physiological properties, attempts have been made to determine the molecular structure of this alkaloid by chemical techniques combined with spectrophotometric studies in the infra-red and ultra-violet regions; but no conclusion regarding a structural formula could be reached⁵. Because of the limited success of the chemical and spectrophotometric techniques, a concurrent structure analysis by X-ray diffraction was initiated when a suitable ‘heavy-atom’ derivative was available. The methiodide of the alkaloid was unsuitable for X-ray analysis because it crystallized in very fine needles and was optically active. However, when cryptopleurine methiodide was boiled with 20 per cent aqueous potassium hydroxide and recrystallized from water, suitable crystals of an isomerized and racemized product, dl-isocryptopleurine methiodide, were obtained⁵. It was this latter compound which was subjected to analysis.