A chiral ligand mediated aza-conjugate addition strategy for the enantioselective synthesis of β-amino esters that contain hydrogenolytically sensitive functionality

Aza-conjugate addition of the lithium anion of N-trimethylsilyl-p-methoxybenzylamine to tert-butyl enoate acceptors, in the presence of a stoichiometric amount of enantiopure 1,2-dimethoxy-1,2-diphenylethane and excess trimethylsilyl chloride, affords tert-butyl-N-p-methoxybenzyl-β-amino esters with excellent levels of enantiocontrol. These N-p-methoxybenzyl-β-amino-esters may be deprotected under oxidative conditions via treatment with ceric ammonium nitrate, followed by acid hydrolysis of the resultant imine intermediates, to afford enantiopure β-amino-esters containing hydrogenolytically sensitive functionality.