Halohydrins of antirrhinoside - the correct structures of muralioside and epimuralioside.

Henrik Franzyk, Søren Rosendal Jensen, Zia Thale, Carl-Erik Olsen

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    Reaction of the iridoid glucoside antirrhinoside (1) with pyridinium chloride in dimethylformamide gave rise to the two possible trans-halohydrins linarioside (4) and isolinarioside (5). Pyridinium bromide gave the two analogous bromohydrins. It is shown that the iridoid glucosides 8-epi-muralioside from Linaria arcusangeli and 7,8-epi-antirrhinoside from L. dalmatica are both identical with isolinarioside and therefore these names are redundant. The structure of muralioside isolated from Cymbalaria muralis is revised to that of its 8-epimer (8) while the structure of an isomeric, new iridoid glucoside from Paulownia tomentosa has been elucidated to be 7beta-hydroxyharpagide (3), the structure originally assigned to muralioside. In addition, 7alpha-hydroxyharpagide (2), the known product from the base-catalyzed hydrolytic opening of 1, has been isolated from Antirrhinum majus and thus shown to be a natural product.
    Original languageEnglish
    JournalJournal of Natural Products
    Issue number2
    Pages (from-to)275-278
    Publication statusPublished - 1999

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