Asymmetric synthesis of R-β-amino butanoic acid and S-β-tyrosine: Homochiral lithium amide equivalents for Michael additions to α,β-unsaturated esters.
Davies SG., Ichihara O.
Michael addition of the lithium amide derived from R-N-(α-methylbenzyl)benzylamine to benzyl E-crotonate is highly stereoselective (95% d.e.) giving after debenzylation and crystallisation homochiral R-β-amino butanoic acid. A similar addition to methyl E-(p-benzyloxy)cinnamate is completely stereoselective giving after debenzylation and acid hydrolysis homochiral S-β-tyrosine as its HCl salt. © 1993.