outcome of the alkylation of a variety of phenylglycinol-derived oxazolopiperidone lactams is studied. The influence of the configuration of the C-8a stereocenter and the effect of the substituents at the C-8 and C-8a positions on the stereoselectivity of the reaction are discussed. The synthetic utility of these alkylation reactions is illustrated with the synthesis of cis and trans 3,5-disubstituted, 2
racemic aryl-delta-oxoacids with (R)-phenylglycinol stereoselectively affords chiral non-racemic bicyclic lactams, from which the enantiodivergent synthesis of (R)- and (S)-2-phenylpiperidine, the diastereodivergent synthesis of cis- and trans-3-ethyl-2-phenylpiperidine, and the enantioselectivesynthesis of the piperidine alkaloid (-)-anabasine is reported.
An Enantioselective Synthetic Route to <i>cis</i>-2,4-Disubstituted and 2,4-Bridged Piperidines
作者:Mercedes Amat、Maria Pérez、Annamaria T. Minaglia、Joan Bosch
DOI:10.1021/jo801172b
日期:2008.9.1
A synthetic route to enantiopure cis-2,4-disubstituted and 2,4-bridged piperidines is reported, the key step being a stereoselective conjugate addition of an organocuprate to a phenylglycinol-derived unsaturated lactam bearing a substituent at the 8a-position.
Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of Piperidines
A straightforward procedure for the synthesis of enantiopure polysubstituted piperidines is reported. It involves the direct generation of chiral non-racemic oxazolo[3,2-a]piperidone lactams that already incorporate carbon substituents on the heterocyclic ring and the subsequent removal of the chiralauxiliary. The key step is a cyclocondensation reaction of (R)-phenylglycinol or other amino alcohols