Reduction of carbonyl compounds via hydrosilylation. 3. Asymmetric reduction of keto esters via hydrosilylation catalyzed by a rhodium complex with chiral phosphine ligands
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)
The asymmetric hydrogenation of α-keto esters catalyzed by rhodium(I) complexes with chiral diphosphine ligands. On the catalytic cycles and the mechanism of asymmetric induction
作者:Iwao Ojima、Tetsuo Kogure
DOI:10.1016/s0022-328x(00)90008-1
日期:1980.8
ketopantoyl lactone catalyzed by rhodiumcomplexes with (—) DIOP and BPPM were carried out under a variety of conditions. It was found that i) the Schrock-Osborn mechanism was not operative in these reactions at all since no acceleration of the reaction rate by the addition of water (1%) was observed, ii) there was a clear difference between cationic and neutral (in situ) rhodium catalysts in their
Lipase-Catalyzed Oligomerization and Hydrolysis of Alkyl Lactates: Direct Evidence in the Catalysis Mechanism That Enantioselection Is Governed by a Deacylation Step
l-lactates in similar conditions. Lipase-catalyzed hydrolysis of alkyl d- and l-lactates was also examined, revealing that the hydrolysis took place for both d- and l-lactates, although l-lactates proceeded a couple of times slower. The hydrolysis results clearly demonstrate that the lipase catalysis mechanism involves an acyl-enzymeintermediate (EM) formation via the acylation step from both d- and
Enantioselective hydrogenation of pyruvates over polymer-stabilized and supported platinum nanoclusters
作者:Xiaobin Zuo、Hanfan Liu、Dawei Guo、Xiaozhen Yang
DOI:10.1016/s0040-4020(99)00415-9
日期:1999.6
cinchonidine-modified enantioselectivehydrogenation of pyruvates has been studied over polyvinylpyrrolidone-stabilized platinum (PVP-Pt) and the corresponding alumina-supported platinum (Al2O3-Pt) clusters. It is shown that the catalysts with particle size less than 2.0 nm demonstrate > 90% enantioselectivity in favor of (R)-lactates. The solvent effect is similar to that over the conventional supported platinum catalyst
已经在聚乙烯吡咯烷酮稳定的铂(PVP-Pt)和相应的氧化铝负载的铂(Al 2 O 3 -Pt)簇上研究了丙酮酸的辛可尼定修饰的对映选择性氢化。结果表明,粒径小于2.0 nm的催化剂表现出> 90%的对映选择性,有利于(R)-乳酸。除四氢呋喃外,其溶剂作用与常规负载铂催化剂相似。这些胶体和负载簇稳定,即使在室温下在空气中放置18个月也没有明显的活性和对映选择性损失。铂表面改性剂-反应物相互作用的分子力学计算表明,可以在小簇上获得良好的对映选择性。
Highly Effective Catalytic Asymmetric Hydrogenations of α-Keto Esters and an α-Keto Acetal with New Neutral Chiral Pyrrolidinebisphosphine-Rhodium Complexes
Synthesis of new chiral pyrrolidinebisphosphine–rhodium complexes and their application to the asymmetric hydrogenations of α-ketoesters and an α-keto acetal are described. Among them, MCCPM-Rh gave the highest optical yield (87%) of the α-hydroxy ester and MCPM-Rh gave the 75% optical yield of the α-hydroxy acetal at the substrate to catalyst ratio (1000:1).