An efficient synthesis of enantiomerically pure (R)-pipecolic acid, (S)-proline, and their N-alkylated derivatives.

Enantiomerically pure (R)-(+)-pipecolic acid was synthesized in four steps and 42% overall yield starting from dihydropyran and (R)-alpha-methylbenzylamine. A general short strategy is also described for preparing (S)-proline (47.5% overall yield) and derivatives.