33942-01-7Relevant articles and documents
Lipase mediated enzymatic kinetic resolution of phenylethyl halohydrins acetates: A case of study and rationalization
Fonseca, Thiago de Sousa,Vega, Kimberly Benedetti,da Silva, Marcos Reinaldo,de Oliveira, Maria da Concei??o Ferreira,de Lemos, Telma Leda Gomes,Contente, Martina Letizia,Molinari, Francesco,Cespugli, Marco,Fortuna, Sara,Gardossi, Lucia,de Mattos, Marcos Carlos
, (2020/02/18)
Racemic phenylethyl halohydrins acetates containing several groups attached to the aromatic ring were resolved via hydrolysis reaction in the presence of lipase B from Candida antarctica (Novozym 435). In all cases, the kinetic resolution was highly selective (E > 200) leading to the corresponding (S)-β-halohydrin with ee > 99 %. However, the time required for an ideal 50 % conversion ranged from 15 min for 2,4-dichlorophenyl chlorohydrin acetate to 216 h for 2-chlorophenyl bromohydrin acetate. Six chlorohydrins and five bromohydrins were evaluated, the latter being less reactive. For the β-brominated substrates, steric hindrance on the aromatic ring played a crucial role, which was not observed for the β-chlorinated derivatives. To shed light on the different reaction rates, docking studies were carried out with all the substrates using MD simulations. The computational data obtained for the β-brominated substrates, based on the parameters analysed such as NAC (near attack conformation), distance between Ser-O and carbonyl-C and oxyanion site stabilization were in agreement with the experimental results. On the other hand, the data obtained for β-chlorinated substrates suggested that physical aspects such as high hydrophobicity or induced change in the conformation of the enzymatic active site are more relevant aspects when compared to steric hindrance effects.
Synthesis of chiral aromatic alcohols: Use of new C2-symmetric RhIIICp*, RuII(cymene), or RuII(benzene) complexes containing chiral diaminocyclohexane ligand as asymmetric transfer hydrogenation catalyst
Montalvo-Gonzalez, Ruben,Chavez, Daniel,Aguirre, Gerardo,Parra-Hake, Miguel,Somanathan, Ratnasamy
experimental part, p. 2737 - 2746 (2009/12/06)
Twelve chiral secondary alcohols were synthesized by asymmetric transfer hydrogenation (ATH) using C2-symmetric bis(sulfonamide) ligand (2) derived from (1R,2R)-cyclohexane-1,2-diamine and complexed with [RhCl 2CP*]2, [RuCl2(cymene)] 2, or [RuCl2(benzene)]2 and then used in situ in the reduction of prochiral ketones. The alcohols were obtained in 85-99% yield and 90-99% enantioselectivity with isopropanol as the hydrogen source. Two-fold rate enhancement and better yields were achieved (88-99%) with 80-99% enantioselectivity using the complex [RhCl2CP*] 2 and aqueous sodium formate as the hydrogen source.
Increased enantioselectivity and remarkable acceleration of lipase-catalyzed transesterification by using an imidazolium PEG-Alkyl sulfate ionic liquid
Itoh, Toshiyuki,Matsushita, Yuichi,Abe, Yoshikazu,Han, Shi-Hui,Wada, Shohei,Hayase, Shuichi,Kawatsura, Motoi,Takai, Shigeomi,Morimoto, Minoru,Hirose, Yoshihiko
, p. 9228 - 9237 (2007/10/03)
Several types of imidazolium salt ionic liquids were prepared derived from poly(oxyethylene)alkyl sulfate and used as an additive or coating material for lipase-catalyzed transesterification in an organic solvent. A remarkably increased enantioselectivity was obtained when the salt was added at 3-10 mol % versus substrate in the Burkholderia cepacia lipase (lipase PS-C)-catalyzed transesterification of 1-phe nylethanol by using vinyl acetate in diisopropyl ether or a hexane solvent system. In particular, a remarkable acceleration was accomplished by the ionic liquid coating with lipase PS in an iPr2O solvent system while maintaining excellent enantioselectivity; it reached approximately 500- to 1000-fold acceleration for some substrates with excellent enantioselectivity. A similar acceleration was also observed for IL1-coated Candida rugosa lipase. MALDITOF mass spectrometry experiments of the ionic-liquid-coated lipase PS suggest that ionic liquid binds with lipase protein.
