5a Crsoxystricrosidire: A Possible Intermediate in the Diogenes's of Insole Alkaloids

Abstract

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The isolated and characterization of three amino acid glycosides from the roots of Rhazya orientalis are described. The relative stereochemistry of 5 a - carboxystrictosidine is determined by NMR and thermodynamic correlations with model compounds. The absolute stereochemistry of 5 a -carboxystrictosidine is established by molar rotation comparisons and biosynthesis and that of strictosamic acid by conversion into strictosidine. The macro-isolation of secologanin is described. Secologanin is used for the partial synthesis of the diastereoisomers of 5 a - carboxystrictosidine. Conformational analysis and the chemistry of these compounds leading to the assignments of their absolute configurations are presented. Final proof of the complete stereochemistry of 5 a – carboxystrictosidine and 5 a - carboxystrictosamic acid came from a direct comparison. The absence of vincoside and 5 – carboxyvincoside in Rhazya orientalis is demonstrated by radio – chemical dilution analysis. The biosynthesis of 5 a – carboxystrictosidine from loganin and L – tryptophan is established and it’s possible biogenetic significance is discussed.