Asymmetric synthesis of R-β-amino butanoic acid and S-β-tyrosine: Homochiral lithium amide equivalents for Michael additions to α,β-unsaturated esters.
摘要:
Michael addition of the lithium amide derived from R-N-(alpha-methylbenzyl)benzylamine to benzyl E-crotonate is highly stereoselective (95% d.e.) giving after debenzylation and crystallisation homochiral R-beta-amino butanoic acid. A similar addition to methyl E-(p-benzyloxy)cinnamate is completely stereoselective giving after debenzylation and acid hydrolysis homochiral S-beta-tyrosine as its HCl salt.
Homochiral lithium amides for the asymmetric synthesis of β-amino acids
作者:Stephen G. Davies、Narciso M. Garrido、Dennis Kruchinin、Osamu Ichihara、Luke J. Kotchie、Paul D. Price、Anne J. Price Mortimer、Angela J. Russell、Andrew D. Smith
DOI:10.1016/j.tetasy.2006.05.008
日期:2006.7
Secondary homochiral lithium amides derived from α-methylbenzylamine undergo highly diastereoselective conjugate additions to a range of α,β-unsaturated esters. The corresponding β-aminoacids are readily liberated by successive N-debenzylation and ester hydrolysis, furnishing (R)-β-amino butyric acid, (R)-β-amino pentanoic acid, (S)-β-leucine, (R)-β-amino octanoic acid, (S)-β-phenylalanine, (S)-β-tyrosine