131234-99-6Relevant articles and documents
General Method for the Asymmetric Synthesis of anti-Diastereoisomers of β-Substituted L-2-Aminobutanoic Acids via Chiral Nickel(II) Schiff's Base Complexes of Dehydroaminobutanoic Acid. X-Ray Crystal and Molecular Structure of the Nickel(II) Complex of the Schiff's Base from <(Benzyl...
Belokon', Yuri N.,Sagyan, Ashot S.,Djamgaryan, Silva A.,Bakhmutov, Vladimir I.,Vitt, Sergei V.,et al.
, p. 2301 - 2310 (2007/10/02)
An efficient approach to the asymmmetric synthesis of (L)-allo-isomers of β-substituted α-aminobutanoic acid is described.The chiral NiII complex of a Schiff's base derived from (S)-o-benzophenone (BBP) and glycine was treated with acetaldehyde in MeOH.The addition proceeds with high diastereoselectivity to give, if catalysed by MeONa, the corresponding complex of (R)-threonine, and, if catalysed by Et3N, the corresponding complex of (S)-allo-threonine.The (R)-threonine complex was converted into the chiral NiII complex of dehydroaminobutanoic acid, and a X-ray diffraction structural study of its major isomer showed that the dehydroaminobutanoic acid moiety was in the E-configuration.The complex, in turn, entered into Michael addition reactions with nucleophiles, including MeOH, EtOH, PhSH, and PhCH2SH.The reaction proceeded with high diastereoselectivity, producing predominantly complexes of the allo-threonine derivatives (d.e. > 90percent).Diastereoisomerically and enantiomerically pure α-amino acids were obtained after chromatographic purification, decomposition of the complexes, and recovery of the initial chiral auxiliary, BBP.The thiol addition reaction is accompanied by a side reaction leading to the formation of sizeable amounts of the vinylglycine complex.An approach to the synthesis of optically active vinylglycine starting with racemic methionine is described.
