THE STRUCTURE OF MITRAPHYLLINE

Abstract

Mitraphylline (C₂₁H₂₄O₄N₂) contains a carbomethoxyl group, and on hydrolysis gives rise to mitraphyllic acid. Spectroscopic evidence shows that the alkaloid contains two chromophores, one characteristic of an oxindole and one corresponding to the grouping CH₃OOC—Ć==CH.OR. On treatment with dilute mineral acid the alkaloid gives rise to mitraphyllal (C₁₉H₂₄O₃N₂), which is a hemiacetal that no longer contains the isolated double bond and the carbomethoxyl group originally present in the alkaloid. Reduction of mitraphyllal by the Wolff–Kishner reaction gives mitraphyllane (C₁₉H₂₆O₂N₂). The dehydrogenation of mitraphyllal produced 3,4-diethylpyridine and 3-ethyloxindole. The action of lithium aluminum hydride on mitraphylline under mild conditions gave rise to mitraphyllol by reduction of the carbomethoxyl group, and under more vigorous conditions to dihydrodesoxy-mitraphyllol by reduction of the oxindole carbonyl as well. This last product has the properties of an aromatic amine. On the basis of the new experimental evidence, a total structure of mitraphylline is derived.