The circular dichroism and optical rotatory dispersion of protoberberines

Abstract

Circular dichroism and optical rotatory dispersion curves of protoberberines and the corresponding benzyltetrahydroisoquinolines have been measured. Allotment of absolute configuration cannot be made by direct comparison between members of the two series, since for the same absolute configuration the two series show curves of opposite signs.

Protoberberine alkaloids are formed by the Mannich reaction of benzyltetrahydroisoquinolines with formalin. This reaction gives products of high optical purity, and can therefore be used for the allotment of configuration to protoberberine alkaloids. The stability of the asymmetric centre was confirmed in the present work; tetrahydropapaverine labelled with deuterium at C-1 retained the isotope during the Mannich reaction.