UBC Theses and Dissertations
Studies related to synthesis and biosynthesis of indole alkaloids Nelson, Verner Robert
In Part I of this thesis, an investigation of the reaction of the alkaloid, catharanthine (12), with zinc in glacial acetic acid is presented. Four isomeric carbomethoxydihydrocleavamines (60-63) have been isolated and fully characterized. It is also shown that heating catharanthine in a mixture of acetic acid and sodium borohydride provides a very convenient method for the preparation of the previously unknown 188-carbomethoxy-cleavamine (64). A similar investigation is presented for some related chemistry of the Aspidosperma series. Minovine (72), when heated in a mixture of acetic acid and sodium borohydride, is readily converted to vincaminoreine (71) and vincaminorine. The reversibility of the latter reaction is demonstrated by the transannular cyclization of vincaminoreine to afford minovine. In Part II, Section A, of this thesis, the synthesis of possible precursors of the Aspidosperma, Vinca, and Iboga alkaloids are described. The synthesis of the methyl cyanoacetate adduct (52) and dimethyl maIonic ester adduct (53) was accomplished without difficulty. The other synthetic precursor, 96, was prepared by treating the chloroindolenine, 94, of the tetracyclic indole, 93, with methyl cyanoacetate and triethylamine. In Part II, Section B, of this thesis are also described the biosynthetic studies in Vinca rosea L. and Vinca minor L. plants. The biogenetic importance of the transannular cyclization reaction is described by evaluating appropriate nine-membered ring alkaloids as possible precursors of the Aspidosperma, Vinca, and Iboga alkaloids. To confirm that the transannular cyclization reaction is not important in the plant, a sequential incorporation of DL-tryptophan-3- C into Vinca minor L. plants is presented. The synthetic precursors, 52, 53 and 96, were also evaluated for their biogenetic importance.
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