116611-25-7Relevant articles and documents
GENERAL METHOD FOR THE ASYMMETRIC SYNTHESIS OF α-AMINO ACIDS VIA ALKYLATION OF THE CHIRAL NICKEL(II) SCHIFF BASE COMPLEXES OF GLYCINE AND ALANINE
Belokon, Yuri N.,Bakhmutov, Vladimir I.,Chernoglazova, Nina I.,Kochetkov, Konstantin A.,Vitt, Sergei V.,et al.
, p. 305 - 312 (2007/10/02)
Nickel(II) complexes of Schiff bases derived from (S)-o-benzaldehyde and alanine (3), or (S)-O-benzophenone and alanine (4), or glycine (5) have been used for the asymmetric synthesis of α-amino acids under a variety of conditions.The method of choice consists of the reaction of the corresponding complex with the appropriate alkyl halide in DMF at 25 deg C using solid NaOH as a catalyst.Low diastereoselective excess (d.e.) is observed for the alkylation of complex (3) with benzyl bromide and allyl bromide.Large selectivity (80 percent) is observed for the alkylation of complex (4).Optically pure(R)- and (S)-O-benzyl-α-methyl-α-amino acids were obtained (70-90 percent) after the alkylated diastereoisomeric complexes had been seperated on SiO2 and hydrolysed with aqueous HCl.The initial chiral reagents were recovered (80-92 percent).The alkylation of complex (5) gave (S)-alanine, (S)-valine, (S)-phenylalanine, (S)-tryptophan, (S)-isoleucine, (S)-2-aminohexanoic acid, and 3,4-dimethoxyphenylalanine with optical yields of 70-92 percent.The optically pure α-amino acids were obtained after the separation of the alkylated diastereoisomeric complexes on SiO2.The stereochemical mechanism of the alkylation reaction is discussed.
