Enzyme catalysed formation of (S)-cyanohydrins derived from aldehydes and ketones in a biphasic solvent system
作者:Herfried Griengl、Norbert Klempier、Peter Pöchlauer、Michael Schmidt、Nongyuan Shi、Antonina A Zabelinskaja-Mackova
DOI:10.1016/s0040-4020(98)00901-6
日期:1998.11
By employing a vigorously stirred two phase system aqueous buffer/organic solvent and using the hydroxynitrilelyase from Hevea brasiliensis as biocatalyst enantiopure (S)-cyanohydrins from aliphatic, unsaturated, aromatic and heteroaromatic aldehydes and methyl alkyl and methyl phenyl ketones are obtained in high yield and in general 98–99% enantiomeric excess.
A simple separation method for (S)-hydroxynitrile lyase from cassava and its application in asymmetric cyanohydrination
作者:Zubiao Zheng、Yan Zi、Zhongzhou Li、Xinzhuo Zou
DOI:10.1016/j.tetasy.2013.03.015
日期:2013.4
Using an acetone precipitation method, crude (S)-hydroxynitrile lyase [(S)-MeHNL] was separated from Munihot esculenta (cassava) leaves, and used directly as biocatalyst to catalyze asymmetric cyanohydrination and produce cyanohydrins with enantiomeric purities (>= 90% ee) significantly greater than those previously reported. The use of a water/i-Pr2O system with an enzyme, NaCN, and appropriate amounts of acetic acid is crucial in improving the stereoselectivity of cyanohydrin formation by minimizing the non-enzymatic reaction and the racemization of the chiral products. The proposed isolation method for crude (S)-MeHNL has a high value because of its simplicity, and low cost as well as the high activity of the crude (S)-MeHNL. (C) 2013 Elsevier Ltd. All rights reserved.
Stereoselective synthesis of thienyl and furyl analogues of ephedrine
作者:Franz Effenberger、Joachim Eichhorn
DOI:10.1016/s0957-4166(96)00528-9
日期:1997.2
The stereoselective syntheses of thienyl and furyl analogues of ephedrine starting from (R)- and (S)-cyanohydrins, respectively, are described. Addition of methyl Grignard to the O-trimethylsilyl protected optically active cyanohydrins (R)- and (S)-3 and hydrogenation of the resulting imino intermediates gives the erythro-2-amino alcohols 4 with high diastereoselectivity. Their reductive methylation
phosphoric acids (CPAs) and their salts are the privileged catalysts in a plethora of asymmetric transformations. All of the scaffolds of efficient CPAs rely on C2-symmetry and axial chirality, while the only examples of punctually chiral CPAs are TADDOL derivatives. Herein, we present the design and the synthesis of C2-symmetric cycloglycerophosphates (cGPAs) and their application throughout the addition