The synthesis of two 2-azetidinones possessing powerful cholesterol-absorption inhibitionproperties has been accomplished by a short and highly stereoselective reaction sequence. The key step is the condensation of the titanium enolate of the easily prepared 2-pyridylthioester (R)-11 with imine 6 which affords the desired β-lactam intermediate in the correct relative and absolute configuration. Conversion
Palomo, Claudio; Cossio, Fernando P.; Cuevas, Carmen, Bulletin des Societes Chimiques Belges, 1992, vol. 101, # 7, p. 541 - 554
作者:Palomo, Claudio、Cossio, Fernando P.、Cuevas, Carmen、Ontoria, Jesus M.、Odriozola, Jose M.、Munt, Simon
DOI:——
日期:——
Stereoselective synthesis of .beta.-lactams by condensation of titanium enolates of 2-pyridyl thioesters with imines
作者:Rita Annunziata、Mauro Cinquini、Franco Cozzi、Pier Giorgio Cozzi
DOI:10.1021/jo00041a019
日期:1992.7
A mild and versatile one-pot synthesis of beta-lactams has been performed by condensation of the easily generated titantium enolates of 2-pyridyl thioesters with imines employing chiral reaction partners. Both imines obtained from enantiomerically pure alkoxy aldehydes and the enolate derived from 3-hydroxybutyrate showed high diastereofacial preferences, efficiently transferring the stereochemical information to the stereocenters of the azetidinone ring. Advanced precursors of (+)-PS-5, (+)-PS-6, thienamycin, and 1-beta-methylthienamycin were prepared to illustrate the potential of this method. A H-1-NMR study of the enolization process and a tentative rationalization of the stereochemical results are presented.