Halogenation reactions of vindoline and 14,15-dihydrovindoline and its hydrochloric
salt were investigated and the anomalous reductions were discussed. Performing
the hydrogenation in the presence of chlorine-containing solvent, e.g. dichloromethane,
hydrogenolysation reaction of chlorine also took place. In this case unexpected chlorinated
product could be observed. Performing the hydrogenation reaction only in the presence
of methanol, the expected reduced derivative was obtained. Upon bromination of
vindoline with excess NBS, oxidation products with ring contraction and developing an
oxygen bridge were isolated. The fluorination reactions of vinblastine using Selectfluor®
and xenon difluoride as the fluorination reagents were unsuccessful because of the decomposition
of the starting material. Reactions of vindoline with Selectfluor® a mixture
of products were obtained. Using xenon difluoride as fluorination agent resulted in a pure quinoidal product
containing the fluorine atom in the bridgehead carbon atom of the indole ring. The fluorination of catharanthine
gave an anomalous indolenine type product.
Keywords: Vindoline, catharanthine, halogenation, Selectfluor®, xenon difluoride, quinoidal products.
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