Wardrop DJ, Bowen EG. Nitrenium ion-mediated alkene bis-cyclofunctionalization: total synthesis of (-)-swainsonine.
Org Lett 2011;
13:2376-9. [PMID:
21486077 PMCID:
PMC3100185 DOI:
10.1021/ol2006117]
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Abstract
The total synthesis of (-)-swainsonine from 2,3-O-isopropylidene-D-erythrose in 12 steps and an overall yield of 28% is reported. The pivotal transformation in our route to this indolizidine alkaloid is the formation of the pyrrolidine ring and C-8a/8 stereodiad through the diastereoselective, bis-cyclofunctionalization of an γ,δ-unsaturated O-alkyl hydroxamate. This transformation is believed to proceed via the intramolecular capture of an N-acyl-N-alkoxyaziridinium ion generated by the diastereoselective addition of a singlet acylnitrenium ion to the pendant alkene.
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