letter	Synlett 1996; 1996: 981-982 DOI: 10.1055/s-1996-5646
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Synthesis of (±)-Indolizidine 209B and a New 209B Diastereoisomer
Joseph P. Michael*, David Gravestock
*Centre for Molecular Design, Department of Chemistry, University of the Witwatersrand, P. O. Wits 2050, South Africa, Fax (+ 27) 11 339 7967, E-mail jmichael@aurum.chem.wits.ac.za

Eight-step syntheses of the frog skin toxin (±)-indolizidine 109B (1) and its hitherto unknown (5R*,8S*,9S*) diastereoisomer (14) via vinylogous urethane intermediates are described. Control of the relative stereochemistry is achieved by alternative stereoselective reductions of a common intermediate, the bicyclic vinylogous urethane 9.

alkaloid - enaminone - indolizidine - sulfide contraction - vinylogous urethane