已经合成了以下系列的新型铁电液晶,它们源自 (R)-3-羟基丁酸的正烷基酯,并研究了决定其介晶特性的几个因素:(备注:省略了图形。)的近晶多态性这些具有三个芳环的化合物受核心中连接基团的位置和种类的影响很大。从结构的角度讨论了两个末端链的长度 (m,n) 和核心中的连接基团对近晶 A 和手性近晶 C 相热稳定性的影响。
Enhanced enantioselectivity in the heterogeneous catalytic hydrogenation of acetoacetate esters into the corresponding 3-hydroxybutyrates using commercial nickel powder
摘要:
Heterogeneous catalytic hydrogenation of acetoacetic acid esters over tartaric acid/NaBr-modified Ni powder was determined to be a critical function of the steric bulk of the ester moiety to afford quantitatively 3-hydroxybutyrate in 94% enantiomeric excess when ethyl and i-butyl esters are used, providing a facile route to optically active 3-hydroxybutyrates. (C) 2014 Elsevier Ltd. All rights reserved.
Poly(3-hydroxybutyrate)-depolymerase from <i>Pseudomonas lemoignei</i>: Catalysis of Esterifications in Organic Media
作者:Ajay Kumar、R. A. Gross、D. Jendrossek
DOI:10.1021/jo000814y
日期:2000.11.1
lemoignei in organic media to catalyze ester-forming reactions was investigated. The effect of different organicsolvents (benzene-d(6), cyclohexane-d(12), and acetonitrile-d(3)) on the activity of the PHB-depolymerase toward propylation of L-lactide was studied. A significant difference in the catalytic rate was observed as a function of solvent polarity. The selectivity of the PHB-depolymerase (P. lemoignei)
Biochemical Reduction of 3-Oxoalkanoic Esters by a Bottom-fermentation Yeast,<i>Saccharomyces cerevisiae</i>IFO 0565
作者:Naoki Mochizuki、Takeshi Sugai、Hiromichi Ohta
DOI:10.1271/bbb.58.1666
日期:1994.1
The scope and limitation of a bottom-fermentation yeast (Saccharomyces cerevisiae IFO 0565) toward the reduction of 3-oxoalkanoic esters were examined. The substrate specificity of this microorganism for various kinds of 3-oxoalkanoic esters was studied. This microorganism was distinct from converntional bakers’ yeast in terms of its selectivity in the reduction and its high expression of a hydrolytic enzyme. 3-Oxoalkanoic ester with an aromatic substituent, a halogen substituted 3-oxoalkanoic ester, an aliphatic longer-chain 3-oxoalkanoic ester and its α,α-difluoro analog were also accepted by this microorganism. The products are useful intermediates in the synthesis of physiologically active compounds.
Enzyme stereoselectivitycontrol is still a major challenge. To gain insight into the molecular basis of enzyme stereo‐recognition and expand the source of antiPrelog carbonyl reductase toward β‐ketoesters, rational enzyme design aiming at stereoselectivity inversion was performed. The designed variant Q139G switched the enzyme stereoselectivity toward β‐ketoesters from Prelog to antiPrelog, providing
酶的立体选择性控制仍然是主要挑战。为了深入了解酶立体识别的分子基础,并将antiPrelog羰基还原酶的来源扩展至β-酮酸酯,进行了针对立体选择性反转的合理酶设计。设计的Q139G变体将酶对β-酮酸酯的立体选择性从Prelog切换为antiPrelog,从而提供了相应的具有高对映体纯度(89.1–99.1%ee)的醇。更重要的是,在立体选择性和活性之间未找到众所周知的折衷方案。Q139G表现出比野生型酶更高的催化活性,提高了催化效率(k cat / K m)从1.1到27.1倍不等。有趣的是,突变体Q139G并未导致对芳族酮的立体选择性反转。酶-底物复合物的分析表明,β-酮酸酯的结构柔韧性和新形成的空穴共同促进了抗Prelog-首选构象的形成。相比之下,芳族酮的相对较大和刚性的结构阻止了它们形成抗Prelog优先的构象。
Asymmetric visible-light photobiocatalytic reduction of β-keto esters utilizing the cofactor recycling system in Synechocystis sp. PCC 6803
The asymmetric reduction of beta-keto esters employing a wild-type strain of cyanobacterium Synechocystis sp. PCC 6803 under illumination of red LED light at 25 degrees C for 24 h was evaluated. As a result, the corresponding (R)-beta-hydroxy esters were obtained as major products. The R-selectivity was shown to increase for bulkier substrates. Moreover, it was also found that the R-selectivity increased with decreasing substrate concentrations. This can be explained by the assumption that the Km value of the R-selective reductase is smaller than that of the S-selective enzyme involved in the reaction. Additionally, it was demonstrated that the R-selective reductase required the light-dependent production of reduced nicotinamide adenine dinucleotide phosphate (NADPH) for effective reaction; however, the S-selective variant did not. Overall, cyanobacterium was employed as a sustainable photobiocatalyst proliferating under illumination of light, while utilizing inorganic salts and atmospheric carbon dioxide (CO2). Employing the whole-cell system allowed for the preparation of industrially-important chiral compounds, such as optically active beta-hydroxy esters. (C) 2020 Elsevier Ltd. All rights reserved.
Enhanced enantioselectivity in the heterogeneous catalytic hydrogenation of acetoacetate esters into the corresponding 3-hydroxybutyrates using commercial nickel powder
Heterogeneous catalytic hydrogenation of acetoacetic acid esters over tartaric acid/NaBr-modified Ni powder was determined to be a critical function of the steric bulk of the ester moiety to afford quantitatively 3-hydroxybutyrate in 94% enantiomeric excess when ethyl and i-butyl esters are used, providing a facile route to optically active 3-hydroxybutyrates. (C) 2014 Elsevier Ltd. All rights reserved.