A highly efficient synthesis of the keyintermediate 2 of 1β-methylcarbapenems was accomplished in 10 steps and 30% overall yield starting from commercially available ()-methyl 3-hydroxy-2-methylpropionate. The explored synthetic scheme features the addition reaction of diketene with a chiral imine as a key diastereoselective step.
Highly diastereoselective synthesis of β-lactams by addition of titanium enolates of 2-pyridyl thioesters to chiral imines
作者:Rita Annunziata、Mauro Cinquini、Franco Cozzi、Pier Giorgio Cozzi
DOI:10.1016/s0040-4039(00)91874-4
日期:1992.2
Addition of titanium enolates of 2-pyridyl thioesters to chiral imines derived from alkoxy aldehydes occurs with good diastereofacial control, and opens a simple access to important carbapenem antibiotics.
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.