N-Boc-2-acyl oxazolidine methodology combined with ring-closing metathesis:: a new approach towards the enantioselective synthesis of α-(1-hydroxyalkyl) nitrogen heterocycles

A synthetic methodology, based on N-Boc-2-acyloxazolidine chemistry combined with ring-closing metathesis, allows the preparation of enantiopure piperidinic heterocycles showing a 2-(1-hydroxyalkyl) side-chain, a pattern commonly found in natural alkaloids. Synthesis of Delta -3,4-2,6-disubsrituted piperidinic rings can thus be achieved with a good 2,6-cis or -trans stereocontrol, unless the substituent located at Ct is not a phenyl group. Diastereoselective functionnalization of the Delta -3,4 alkene moiety and access to seven or eight-membered nitrogen rings are also key features of this methodology. (C) 2001 Elsevier Science Ltd. All rights reserved.