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
Conjugate Additions to Phenylglycinol-Derived Unsaturated δ-Lactams. Enantioselective Synthesis of Uleine Alkaloids
作者:Mercedes Amat、Maria Pérez、Núria Llor、Carmen Escolano、F. Javier Luque、Elies Molins、Joan Bosch
DOI:10.1021/jo0487101
日期:2004.12.1
sulfur-stabilized anions) to the phenylglycinol-derived unsaturated lactams trans-2, cis-2, and its 8-ethyl-substituted analogue 10 is studied. The factors governing the exo or endo facial stereoselectivity are discussed. This methodology provides short synthetic routes to either cis- or trans-3,4-disubstituted enantiopure piperidines as well as efficient routes for the enantioselective construction of the tetracyclic
Highly enantioselective dynamic kinetic resolution and desymmetrization processes by cyclocondensation of chiral aminoalcohols with racemic or prochiral δ-oxoacid derivatives
作者:Mercedes Amat、Oriol Bassas、Miquel A. Pericàs、Mireia Pastó、Joan Bosch
DOI:10.1039/b413937b
日期:——
Cyclocondensation reactions of aminoalcohols and with racemic or prochiral delta-oxoacid derivatives provide polysubstituted lactams with high enantioselectivity in a process that involves dynamic kinetic resolution and/or desymmetrization of enantiotopic or diastereotopic ester groups.
[GRAPHICS]Starting from a common chiral bicyclic lactam 11, enantiopure trans- or cis-3-ethyl-4-piperidineacetate derivatives are obtained by conjugate addition of an enolate or a cuprate to the unsaturated lactams 12 or 18, respectively.