| Abstract
| - The cyclization of γ-chloroamine 11, derived from l-alanine, and acetylenic sulfone 12 afforded thedehydropiperidine 19 via conjugate addition followed by intramolecular alkylation of the correspondingsulfone-stabilized anion. An unexpected acid-catalyzed desulfonylation of 19 occurred in one step viadesilylation and tautomerization of the enamine moiety to the corresponding aldehyde, followed byelimination of p-toluenesulfinic acid. The highly stereoselective reduction of the resulting unsaturatedaldehyde 25 with sodium cyanoborohydride produced piperidine 23 with a diastereomeric ratio of >98:2. (−)-(ent)-Julifloridine (8) was obtained by Swern oxidation of 23, followed by Wittig olefination andhydrogenation/debenzylation.
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