General method for the asymmetric synthesis of α-amino acids via alkylation of the chiral nickel(II ) Schiff base complexes of glycine and alanine
| Autor: | N. S. Garbalinskaya, Vladimir I. Bakhmutov, Konstantin A. Kochetkov, S. V. Vitt, N. I. Chernoglazova, Yuri N. Belokon, V. M. Belikov |
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| Rok vydání: | 1988 |
| Předmět: | |
| Zdroj: | J. Chem. Soc., Perkin Trans. 1. :305-312 |
| ISSN: | 1364-5463 0300-922X |
| DOI: | 10.1039/p19880000305 |
| Popis: | Nickel(II) complexes of Schiff bases derived from (S)-o-[(N-benzylprolyl)amino] benzaldehyde and alanine (3), or (S)-O-[(N-benzylpropyl)amino]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 °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%) is observed for the alkylation of complex (4). Optically pure (R)- and (S)-α-methyl-α-amino acids [(S)-α-methylphenylalanine, (S)-α-allylalanine and (S)-O-benzyl-α-methyltyrosine] were obtained (70–90%) after the alkylated diastereoisomeric complexes had been separated on SiO2 and hydrolysed with aqueous HCl. The initial chiral reagents were recovered (80–92%). The alkylation of complex (5) gave (S)-alanine, (S)-valine, (S)-phenylalanine, (S)-tryptophan, (S)-isoleucine, (S)-2-aminohexanoic acid, and 3,4dimethoxyphenylalanine with optical yields of 70–92%. 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. |
| Databáze: | OpenAIRE |
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