epoxides and L-proline. The key step of this synthesis relied on a diastereoselective intramolecular alkylation of a proline enolate, which led to an azetidine ring fused to a five-membered ring. These strainedbicyclic nitrogen derivatives were found to be good precursors for the preparation of azepanes, after transformation into the corresponding ammonium trifluoromethanesulfonates followed by reaction