Chiral Indolizinium Salts Derived from 2-Pyridinecarbaldehyde-First Diastereoselective Syntheses of (-)-1-epi-lentiginosine

The first diastereoselective synthesis of (-)-1-epi-lentiginosine from a common chiral trans-epoxyamide derived from 2-pyridincarbaldehyde is reported. This methodology involves a sequential oxirane ring opening and intramolecular 5-exo-tet cyclization of tosylate trans-epoxyalcohol to afford a diastereomeric mixture of indolizinium salts in a one-pot fashion, followed by regio- and diastereospecific pyridinium ring reduction.