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Synthesis 1999; 1999(2): 286-289
DOI: 10.1055/s-1999-3396
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Synthesis of Optically Active Indolizidines: (-)-8a-epi-Dendroprimine and (-)-7,8-Dehydro-5,6-dimethylindolizidine

Michel Diederich* , Udo Nubbemeyer
  • *Inst. für Organische Chemie, Freie Universität Berlin, Takustr. 3, D-14195 Berlin; Fax +49(30)8 38 51 63; E-mail: udonubb@chemie.fu-berlin.de
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Publication Date:
31 December 1999 (online)

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Indolizidinones can be employed as key intermediates in efficient asymmetric synthesis of naturally occurring indolizidine alkaloid analogues. The 5,7-dimethylindolizidine (-)-8a-epi-dendroprimine was formed by a diastereoselective methylation-reduction sequence of the lactam function. The (-)-5,6-dimethylindolizidine was generated via the same key step including an additional quasi 1,2-methyl shift: an intramolecular enamine alkylation is followed by regioselective reductive cyclopropane ring opening.

indolizidinone - indolizidine - intramolecular enamine alkylation - iminium salt - diastereoselective reduction - radical cyclopropane opening