| Abstract
| - We report the enantiospecific synthesis of the sterically congested all-cis 2,3,4,5-substitutedpyrrolidines 4, 5, and 6, from either d- or l-serine. Hemiaminal intermediate 13 is converted tothe fully substituted pyrrolidine 15 by way of a tandem Wittig−Michael reaction. The endostereochemistry of the C-3 methyl group of compound 15 is set by stereoselective reduction of thedouble bond in 11, driven by a preference for hydrogenation from the rear side of the molecule.The all-cis configuration of these fully substituted pyrrolidines has been established by X-rayanalysis of compound 6. Removal of the benzenesulfonyl group from the highly substituted andfunctionalized intermediate 15 is successfully accomplished by sodium naphthalenide reduction.
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