Diastereocontrolled reduction of cyclic β-enaminones.: A new diastereoselective route to 2,6-disubstituted piperidines

A new diastereoselective synthesis of 2,6-disubstituted piperidinic alkaloids is presented. Three natural compounds, the (-)-pinidinone 1a, the (+)-dihydiopinidine 1b and the (-)-pinidinol 1c were prepared from optically pure (6R)-6-methylpiperidin-2-one 2. This method is based on thc chemo- and diastereocontrolled reductions of an exocyclic beta -enamino ketone. (C) 2001 Elsevier Science Ltd. All rights reserved.