Constitution of Yohimbine

Abstract

IT has been suggested by D. G. Harvey, E. J. Miller and W. Robson in a recent publication¹ on the colour reactions of tryptophan and allied compounds—among them the alkaloid yohimbine—that the formation of a blue colour in sulphuric acid containing a trace of oxidizing agent is characteristic of the 4–carboxytetrahydro–β–carbolines. The presence in yohimbine of both tetrahydro–β–carboline and carboxylic acid (actually carbomethoxyl) residues has been recognized for some time, and it is clear from the formation in good yields of 2: 3–dimethylbenzoic acid from ketodihydroyobyrine², and of harman and m–toluic acid from tetradehydroyohimbic acid³, that the carbomethoxyl must be attached to the yohimbine skeleton, which is as depicted, in ring E at position 16.