Constituents of Nauclea diderrichii. Part IX. Conversion of sweroside to naucledal and 3-epinaucledal

Abstract

The aglucone of sweroside has been converted to naucledal and its epimer, 3-epinaucledal; the structure and stereochemistry of these products have been established through analysis of their nmr spectra. The course of the rearrangement has been studied and the intermediacy of a ring–opened isomer, seconaucledal, has been demonstrated. The relative amounts of naucledal and 3-epinaucledal produced from seconaucledal depend on the conditions of the cyclization.