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Synthesis and biosynthesis of indole alkaloides.

University of British Columbia

In part A, a much sought synthesis of the calycanthaceous alkaloids is described. Oxidative dimerization of N- methyltrytamine afforded dl- chimonanthine and meso-chimonanthine, and dl- calycanthine was produced by subsequent acid-catalyzed rearrangement of the carbon skeleton through a tetraminodialdehyde. As the suggested biosynthesis of these alkaloids is represented as occurring by an oxidative dimerization of N- methyltryptamine (itself a natural product) the very direct synthesis described is a biosynthetic model. The discovery of meso-chimonanthine in an extract of Calycanthus f1oridus is also reported and is the first natural calycanthaceous alkaloid with this stereochemistry to be discovered. As folicanthine and calycanthidine are N-methyl chimonanthines and this methylation has been reported, a synthesis of chimonanthine also represents a formal synthesis of these alkaloids. A proposal for the structure of hodgkinsine, the remaining calycanthaceous alkaloid, is made. A number of synthetic by-products are also described. In part B evidence for the mono-terpenoid origin of the nine or ten carbon non-tryptophan derived portion of the indole alkaloids is presented. The monoterpene, geraniol- 2- ¹⁴C, was administered to Vinca rosea cuttings and the Aspidosperma- type alkaloid, vindoline, was isolated and shown by Kuhn-Roth degradation to be labelled at C-5 as predicted by theory. Feeding experiments with mevalonic acid- 2- ¹⁴C are also described.

Text

2011-08-30

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http://hdl.handle.net/2429/36984

Chemistry

University of British Columbia

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