From chiral benzylic malonic acid esters (R)-(+)-4, available with high enantiomeric excesses by enzymatic hydrolysis (PLE acetonic powder), enantiomerically enriched pyrrolidinones 1 and pyrrolidines 2 were prepared. This rapid and competitive method was developed via enol ether formation, and subsequent one-pot cyclisation, in good overall yield.
Arzel, P., Freida, V., Weber, P., & Fadel, A. (1999). An easy access to (S)-pyrrolidinones and -pyrrolidines from chiral benzylic malonates. Tetrahedron Asymmetry, 10(20), 3877–3881. https://doi.org/10.1016/S0957-4166(99)00425-5