ASYMMETRIC-SYNTHESIS OF SYN-ALPHA-ALKYL-BETA-AMINO ACIDS

An investigation into the reactivity of the highly stereoselective con jugate nucleophile lithium N-benzyl-N-alpha-methylbenzylamide 1 with a lpha-alkyl-alpha,beta-unsaturated esters has led to the development of a versatile asymmetric synthesis of syn-alpha-alkyl-beta-amino acids. By performing the conjugate additions in toluene and diluting the rea ction mixtures with THF prior to quenching of the reactions with the h indered acid. 2,6-di-tert-butylphenol 13, the product syn-alpha-alkyl- beta-amino esters may be generated in good yield and with excellent st ereocontrol. Several examples illustrate the ease with which these pro ducts may be debenzylated and hydrolysed to afford homochiral syn-alph a-alkyl-beta-amino acids.