Total Syntheses of All Four Isomers of cis- 1,Z-Dihydroxypyrrolizidine

A chemically efficient strategy for the preparation of the four stereoisomers of cis-1,2-dihydroxypyrrolizidine7, ,8, ent-7, and ent-8. The syntheses have been accomplished by divergent routes starting from either enantiomer of glyceraldeyde acetonide, 1 or ent-1, and utilizing N-(tert-butoxycarbonyl)-2-(tert-butyldimethylsiloxy)pyrrole (2), readily obtainable from pyrrole.