STEREOSELECTIVE SYNTHESIS OF BETA-LACTAMS BY CONDENSATION OF TITANIUM ENOLATES OF 2-PYRIDYL THIOESTERS WITH IMINES BEARING A CHIRAL AUXILIARY

Several amines have been tested as chiral auxiliaries in the stereoselective synthesis of beta-lactams by condensation of the titanium enolates of 2-pyridyl thioesters with chiral imines. The amines were selected among the following classes of compounds: benzylic amines, beta-aminoalcohols, beta-heterosubstituted alpha-aminoesters. Inexpensive and available in both enantiomeric forms alpha-methylbenzylamine was identified as the chiral auxiliary that generally combines good reactivity and satisfactory levels of stereocontrol. To illustrate the potential of the method a precursor of a component of a renin inhibitor was prepared. A tentative rationalization of the stereochemical results is presented.