Bakers' yeast reductions of β-oxopyrrolidinecarboxylates: synthesis of (+)-cis-(2R,3S)-3-hydroxyproline and (–)-(1S,5S)-Geissman–Waiss lactone, a useful precursor to pyrrolizidine alkaloids

Abstract

Bakers' yeast reduction of the β-oxo proline derivative 5 leads to the cis-hydroxy ester 6 and thence to (+)-cis-(2R, 3S)-3-hydroxyproline 7, with > 90% enantiomeric enrichment. Subsequent one-carbon homologation leads to the (–)-Geissman–Waiss lactone 8, a useful precursor of pyrrolizidine alkaloids.