Stylopine and Coptisine

The pure optically active forms of stylopine melt at 202° and the pure dZ-form melts at 221°. Mixtures of the racemic with one of the active forms occur in plants and when recrystallized several times often melt at 206°. 

Constitution. Haworth and Perkin (240) had already synthesized dZ-stylopine (dZ-tetrahydrocoptisine) in the course of their synthesis of protopine, but at that time the alkaloid was not recognized as a natural product. When oxidized with iodine it yields coptisine iodide, which has been isolated in this form from Coptis japonica (165). Coptisine is also present in Corydalis ambigua (26), and of course traces could no doubt be found in all plants which contain stylopine. 

Aside from the above-mentioned synthesis the best proof of the structure of stylopine is that of Spath and Posega (241), who reduced protopine to the carbinol, dehydrated this to the quaternary chloride, and then following Perkin s procedure eliminated methyl chloride by distillation in a high vacuum. The resulting product (LI) was identical with dl-tetrahydro- 

It should also be noted that Kitasato (165) demethylenated coptisine to the corresponding tetrahydroxy compound, and this when methylated with diazomethane yielded palmatine. Coptisine is therefore LII. 

The more difficult transformation of four methoxyl groups to two methyl-enedioxy groups was also achieved by Spath and Posega (241). It was possible to demethylate tetrahydropalmatine to the above tetrahydroxy compound, and this was bismethylenated in small yield to stylopine. The reaction was carried out in a sealed tube by heating the base with methylene iodide. 

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