Synthesis of vinca alkaloids and related compounds. Part 109. An intramolecular [4+2] cycloaddition mediated biomimetic synthesis of (?-iboxyphylline.

[摘要]：The pentacyclic alkaloid iboxyphylline could be synthesized by an intramol. [4+2] cycloaddn. of intermediate I, which was obtained from tryptamine II and OCH(CH2)2CH(OAc)CHMeCO2Me. After full epimerization of III the cyclization reaction furnished a mixt. of epimeric 21-oxoiboxyphylline acetates. Sepn. of the stereoisomers and subsequent redn. with LiAlH4 resulted in (?-iboxyphylline and its epimer, (?-20-epiiboxyphylline.

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