Abstract
Four kinds of indole alkaloids, gardneramine, gardnerine, gardnutine and hydroxygardnutine, were isolated from Gardneria nutans SIEB. et ZUCC. (Horaikazura). Among them, gardnerine, gardnutine and hydroxygardnutine were examined and the structures, I, II and III were assigned respectively to gardnerine, gardnutine and hydroxygardnutine on the basis of chemical and physical data. The main alkaloid gardnerine (I) was interrelated with ajmaline (IV)(of established absolute configuration) by two different routes (A and B). In the route A, I was transformed to 1-demethyl-Δ1-17, 21-dideoxyajmaline (XXVIII) which in turn was erived from ajmaline (IV). On the other hand, in the route B, I was transformed to XXXII which in turn was derived from isoajmaline (XXXV)(C20-ethyl epimer of ajmaline). The stereochemistry of the ethylidene side chain of II was determined by NOE measurement. These correlations as well as the nuclear overhauser effect (NOE) experiment established the absolute stereochemistry of I, II and III as shown in Chart 15.
