Isolation and structure elucidation of additional alkaloids from the tropical rainforest tree Galbulimima baccata

Nirmal K. Chaudhary, Walter C. Taylor, Lewis N. Mander, Peter Karuso*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    1 Citation (Scopus)

    Abstract

    The structures of five new natural products (GB 27-GB 31, 1-5), isolated as minor components from the bark of Galbulimima baccata, have been determined by 2D NMR spectroscopy in combination with DFT calculations. Among the alkaloids, GB 31 (5) belongs to Class I, GB 27 (1) and 28 (2) belong to Class II, and GB 30 (4) belongs to Class III GB alkaloids. GB 31 is the first non-nitrogen-containing GB "alkaloid", being a biosynthetic oxidation product of himbacine, himandravine, or himbeline. GB 29 (3) has an entirely new natural product scaffold but belongs to Class IV (miscellaneous alkaloids). The isolation of a new Galbulimima scaffold has revealed a new pathway in the biosynthesis of the GB alkaloids. The new molecules isolated have shed further light on the biogenetic relationship among these structurally unique and complex groups of alkaloids. We present, for the first time, a unified biogenesis for the GB alkaloids that were first isolated in the 1950s and now number over 40 examples. This work also brings full circle the story of Galbulimima alkaloids. A life-long project of Wal Taylor involving one of his first students (Lew Mander) and one of his last students (Peter Karuso), a story stretching over six decades, has come to a final conclusion.

    Original languageEnglish
    Pages (from-to)2525-2535
    Number of pages11
    JournalJournal of Natural Products
    Volume84
    Issue number9
    DOIs
    Publication statusPublished - 24 Sep 2021

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