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UBC Theses and Dissertations

Studies on the biosynthesis of indole alkaloids Beck, John Frank

Abstract

In Section A of this thesis an investigation of the intermediacy of glycine in the biosynthesis of the monoterpenoid C₁₀ unit of the indole alkaloids is described. Utilizing the carbon-14 labelled forms of glycine and plants of Vinca rosea Linn., experiments were carried out on the Corynanthe alkaloid ajmalicine [56]. Degradation of this compound revealed the relative non-importance of glycine in the biosynthesis of the C₁₀ unit. The incorporation of this amino acid into tryptophan [11] and hence into the indole alkaloids was postulated. This postulate has since been confirmed by another laboratory. Section B, provides initially a resume of the synthesis of 16,17-dihydrosecodin-17-ol [114] and of secodine [115]. The biological evaluation of these compounds as potential intermediates in. the later stages of indole alkaloid biosynthesis is described in Sections B, C, and D. Experiments were carried out with the various labelled forms of these two compounds and the plant systems V. rosea, V. minor Linn, and Aspidosperma pyricollum Muell. Arg. Degradation of the alkaloids vindoline [3] and apparicine [144] established the specific incorporation of the indole portion of secodine[115] into these substances. Additional information provided by double isotope studies with ail three plant systems indicated support for the specific incorporation of the entire secodine molecule [115] into several indole alkaloid families. In addition, the evidence obtained strongly suggests the existence of a central common intermediate, which by appropriate enzymatic control at the later stages of the pathway, allows elaboration to the various families of indole alkaloids.

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