Standard Enthalpies of Formation for Solid Complexes of Chromium Chloride with L-α-Amino Acids

The solid complexes of Cr(AA) 2Cl 3·nH 2O of CrCl 3 with L-α-amino acids (AA=Val, Leu, Thr, Met, Arg, Phe, Try and His) have been prepared in 95% EtOH medium, and characterized structurally by elemental analysis, chemical analysis, IR spectra and TG-DTG. The constant-volume combustion energies of the complexes have been determined by RBC-II type rotating-bomb calorimeter. The standard enthalpies of formation of the complexes have been calculated as well, which are ( -2543.16± 3.71) (Val), ( -2561.32± 4.06) (Leu), ( -2284.02± 2.95) (Thr), ( -1418.77± 4.60) (Met), ( -3218.91± 4.67) (Arg), ( -2643.90± 5.02) (Phe), ( -1707.18± 3.23) (Try) and ( -2838.05±3.45) (His) kJ/ mol, respectively.

Synthesis of d,l-α-Tocopherol Catalyzed by Heteropoly Acids

,d,l-a-Tocopherol (vitamin E) isfound to be synthesized by condensingtrimethylhydroquinone with isophytol catalyzed by heteropoly acids (HPA) H3:PW12O40 andH3PMo12O40 at room temperature. These HPA are efficient catalysts for the synthesis of d l-a-Tocopherol and can easily be separated from the reaction mixture and roused,

D-(—)-α-苯甘氨酸的合成

D-(-)-α-苯甘氨酸是合成氨苄青霉素的原料,采用腈化物路线合成其的独到之处是在用L-(+)-酒石酸拆分DL-α-氨基-α-苯乙腈时,往其中加少量催化剂(酮类),可使D-型左旋体的收率提高到80％以上。

L-半胱氨酸衍生物配体交换手性色谱固定相

A novel chiral stationary phase(CysCSP) for ligand exchange chromatography was prepared by firstly synthesizing N,S-di(2-hydroxyl-3-octoxyl)propyl-L-cysteine as chiral selector via reaction of L-cysteine with glycidyl octyl ether and then coating it on YWG-C-{18} bonded stationary phase. The enantiomeric resolutions of some D,L-α-amino acids were achieved on CysCSP by using cupric acetate aqueous solution as the mobile phase, under the conditions of column temperature 20 ℃ and detection at UV 254 nm. The enantioselectivities α of D,L-α-amino acids separated were found to be in the range from 1.11 to 1.38 with the resolution R-s ranging from 1.1 to 2.8 and the column efficiency being from 5 000 to 9 000 n/m. The elution order of D-isomer before L-isomer was obersaved for all D,L-amino acids used.

苏氨酸醛缩酶的研究进展

苏氨酸醛缩酶(TAs)以磷酸吡哆醛为辅酶,催化不同的醛与α-氨基酸发生醇醛缩合反应,形成具有2个手性中心的β-羟基-α-氨基酸。TAs在不对称催化过程中可以控制产物α-碳位的立体构型,而对β-碳位的立体构型控制相对较弱。增强TAs在β-碳位的立体选择性是近年来研究TAs不对称催化的热点。本文重点阐述了TAs的结构与作用机制、定向进化,以及在生物催化合成中的应用,对TAs的研究与开发进行了展望。

苏氨酸醛缩酶的催化机理、分子改造及合成应用

苏氨酸醛缩酶催化醛和甘氨酸羟醛缩合,一步反应即可构建产物β-羟基-α-氨基酸的两个手性中心,从原子经济性和环境影响角度,是非常具有潜力的绿色合成光学纯β-羟基-α-氨基酸的方式之一。多个不同生物来源的苏氨酸醛缩酶得到分离和表征,较低的β-碳立体选择性以及反应过程中动力学和热力学控制难题,使其在合成应用中面临很大挑战。文中综述了近年来苏氨酸醛缩酶在基因挖掘、催化机理、高通量筛选与分子改造、合成应用等方面的研究进展,旨在为进一步研究提供参考。