L. Micouin et al., ASYMMETRIC-SYNTHESIS .40. 2,3-DISUBSTITUTED PIPERIDINES VIA CHIRAL NON-RACEMIC LACTAMS, Tetrahedron letters, 37(6), 1996, pp. 849-852
Optically pure 2,3-cis-disubstituted piperidines 7a and 7b have been p
repared from chiral lactams 2. The first step involves C-2 functionali
zation with Grignard reagent, then a diastereoselective reduction of r
esulting oxazolidines 5 furnishes the desired piperidines 7.