Vu Moc Vu Moc Thuy

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

Abstract A new diastereoselective synthesis of 2,6-disubstituted piperidinic alkaloids is presented. Three natural compounds, the (−)-pinidinone 1a , the (+)-dihydropinidine 1b and the (−)-pinidinol 1c were prepared from optically pure (6 R )-6-methylpiperidin-2-one 2 . This method is based on the chemo- and diastereocontrolled reductions of an exocyclic β-enamino ketone.

New highly enantioselective synthesis of 6-alkylpiperidin-2-ones and 2-substituted piperidines

Abstract A versatile and highly enantioselective approach to 2-substituted piperidines is described using phenylglycinol as chiral auxiliary.

Asymmetric synthesis of (+) and (−) trans-2,6-dimethylpiperidines

Abstract (+) and (−) trans-2,6-dimethylpiperidines 9 have been prepared from diastereomeric lactams 6 and 11, both available from (R)-(−)-phenylglycinol 4. Diastereoselective C-2 alkylation afforded oxazolidines 7 and 12. Reduction of 7 with LiAlH4 or NaBH4 led to trans-2,6-8 with total retention of configuration. When 12 was reduced with NaBH4, trans derivative 13a was isolated as the major isomer. A mechanism is proposed to explain the different results.