期刊
ORGANIC & BIOMOLECULAR CHEMISTRY
卷 2, 期 14, 页码 2044-2049出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/b404381b
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Attempts are made to build a bridge between asymmetric catalysis and enzymatic reactions by mechanistic investigations and the development of a catalytic and enantioselective approach to amination of alpha-keto esters by primary amines catalyzed by chiral Lewis acids as a model for transamination enzymes. Different Lewis acids can catalyze the half-transamination of alpha-keto esters using primary amine nitrogen sources such as pyridoxamine and 4-picolylamine. The mechanistic studies of the Lewis-acid catalyzed half-transamination using deuterium-labelled compounds show the incorporation of deuterium atoms in several positions of the alpha-amino acid derivative, indicating that the enol of the alpha-keto ester plays an important role along the reaction path. The catalytic enantioselective reactions are dependent on the pK(a)-value of the solvent since enantioselectivities were only obtained in solvents with high pK(a)-values relative to methanol. However, stronger acidic conditions generally gave better yields, but poor enantioselectivities. A series of chiral Lewis acids were screened as catalysts for the enantioselective half-transamination reactions and moderate yields and enantioselectivities of up to 46% ee were obtained.
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