Efficient and Expeditious Protocols for the Synthesis of Racemic and Enantiomerically Pure Endocyclic Enecarbamates from <i>N</i>-Acyl Lactams and <i>N</i>-Acyl Pyrrolidines
作者:Denilson F. Oliveira、Paulo C. M. L. Miranda、Carlos R. D. Correia
DOI:10.1021/jo9903297
日期:1999.9.1
A mild, practical, and straightforward protocol for the construction of endocyclic enecarbamates starting from N-acyl lactams and N-acyl pyrrolidines is presented. Lactams were reduced to the corresponding alpha-hydroxycarbamates in good to excellent yields using DIBAL-H, SuperHydride, or NaBH(4) followed by beta-elimination (dehydration) promoted by trifluoroacetic anhydride in the presence of hindered
Diastereofacial selectivity in ketene [2+2] cycloaddition to endocyclic enecarbamates bearing a chiral auxiliary. Synthesis of the (−)-Geissman-Waiss lactone
作者:Paulo Cesar M.L. Miranda、Carlos Roque D. Correia
DOI:10.1016/s0040-4039(99)01638-x
日期:1999.10
evaluated for the [2+2]cycloaddition with dichloroketenes. Diastereofacial selectivity ranged from zero (bornyl and menthyl) to 60% (Greene's auxiliary and 8-phenylmenthyl). Chromatography separation of the diastereomeric azacyclobutanones derived from the 8-phenylmenthyl enecarbamate permitted an enantiodivergent synthesis of the (−)-Geissman-Waiss lactone, a key intermediate in the synthesis of necine bases