97101-16-1Relevant articles and documents
Nonproteinogenic Amino Acids, III. - Syntheses of the Enantiomerically Pure 2-(2-Thienyl)- and 2-(3-Thienyl)glycines. - Molecular Structure of the Intermediate Schiff's Bases
Weinges, Klaus,Brachmann, Helga,Stahnecker, Peter,Rodewald, Hans,Nixdorf, Matthias,Irngartinger, Hermann
, p. 566 - 578 (2007/10/02)
The syntheses of enantiomerically pure D-(-)- and L-(+)-2-(2-thienyl)- and 2-(3-thienyl)glycines (6a-d) are described.Preparing the amino nitriles 4 directly from 2-thiophenecarbaldehyde (1a) or 3-thiophenecarbaldehyde (1b), respectively, and (4S,5S)-(+)-5-amino-2,2-dimethyl-4-phenyl-1,3-dioxane (2), and hydrocyanic acid (one-step procedure), the aminonitriles 4a and 4b, respectively, are formed in excess.By crystallization they are obtained diastereomerically pure leading to enantiomerically pure D-amino acids 6a and 6b.If, however, the intermediate Schiff's bases 3 are isolated as crystals and then converted with hydrocyanic acid into the respective aminonitriles 4 (two-step procedure), the diastereomeric aminonitriles 4c and 4d, respectively, crystallize resulting in enantiomerically pure L-amino acids 6a and 6d.X-ray structure analyses of the Schiff's bases 3c and 3e revealed the previously postulated E-configuration of the C=N bond and its chiral shielding by the phenyl substituent at C4.
