616-51-3Relevant academic research and scientific papers
Asymmetric transesterification of secondary alcohols catalyzed by feruloyl esterase from Humicola insolens
Hatzakis, Nikos S.,Smonou, Ioulia
, p. 325 - 337 (2007/10/03)
A new asymmetric transesterification of secondary alcohols catalyzed by feruloyl esterase from Humicola insolens has been found. Although alcohols are not the natural substrates for this enzyme, a high R enantioselectivity was observed. Stereochemical studies showed that variations in substrate structure lead to strong variations in enantioselectivity. The highest enantioselectivities are obtained when the β-carbon of the secondary alcohol is tertiary or quaternary.
Entrapment of Pseudomonas cepacia lipase with peracetylated β-cyclodextrin in sol-gel: Application to the kinetic resolution of secondary alcohols
Ghanem, Ashraf,Schurig, Volker
, p. 2547 - 2555 (2007/10/03)
Co-lyophilized Pseudomonas cepacia lipase with peracetylated β-cyclodextrin was immobilized by the sol-gel process. The gel-entrapped lipase/cyclodextrin was prepared by the hydrolysis of methyltrimethoxysilane (MTMS) in the presence of the co-lyophilized lipase with peracetylated β-cyclodextrin prepared with different weight ratios (enzyme to CD). This type of enzyme preparation was subsequently used in the kinetic resolution of a set of secondary alcohols using isopropenyl acetate as an innocuous acyl donor in toluene as the organic medium. The resulting chiral alcohols (substrate) and the corresponding acetates (product) were baseline separated in one analysis without derivatization using gas chromatography on a new chiral stationary phase (CSP) Chirasil-β-Dex containing an undecamethylene spacer (C11-Chirasil-Dex).
The Influence of Steric Effects on the Selectivity of Radical CC Bond Formation Reactions
Giese, Bernd,Harnisch, Hanna,Luening, Ulrich
, p. 1345 - 1351 (2007/10/02)
Bulky substituents R1 and R2 at radical 5 decrease the rate of addition to diethyl fumarate to a larger extent than to methyl acrylate (Table 1).The comparison with H-abstraction, which is only slightly influenced by steric effects, shows that 5e (R2 = t-C4H9) reacts at least 235 times slower with diethyl fumarate than 5a (R2 = CH3) (Table 2).Therefore, the stereoselectivity of cyclic radicals 1 (n = 1,2) increases if the CC bond formation reaction is carried out with diethyl fumarate instead of methyl acrylate.
Reactions with Umpolung via Radicals: CC-Bond Formation between Ketones and Alkenes
Giese, Bernd,Erfort, Ulrich
, p. 1240 - 1251 (2007/10/02)
The hydrazones 1 - 11 from ketones react in a general synthetic procedure with alkenes 33a - m to yield products 34 - 44 (table 2 and 3).Important intermediates of these reactions with umpolung are 1-acetoxyalkyl radicals 49 that are formed from organomercuric salts 14 - 24 by reduction with NaBH4.This new CC-bond formation reaction can be carried out in a one-pot synthesis without isolation of the metalorganic compounds (table 4). - In side reactions the reduction products 50 are formed, if bulky starting compounds or less reactive alkenes are used (table 5 and 6).
RATIO OF POLAR AND RADICAL PROCESSES IN THERMAL TRANSFORMATIONS OF PEROXIDES. I. EFFECT OF THE LENGTH AND BRANCHING OF THE CHAIN IN THE ALKYL SUBSTITUENT AT THE α-CARBON ATOM OF THE ACYL GROUP
Stankevich, A. I.,Zyat'kov, I. P.,Lazareva, A. M.,El'nitskii, A. P.
, p. 1543 - 1548 (2007/10/02)
Acetyl 2-methylpropionyl, acetyl 2-methylbutyryl, acetyl 2-methyloctanoyl, acetyl 2,3-dimethylbutyryl, and acetyl 2,3,3-trimethylbutyryl peroxides are transformed thermally under the investigated experimental conditions with the formation of the corresponding acyl alkyl carbonates and radical products.The ratio of the polar and radical processes is affected by the length and branching of the chain in the hydrocarbon substituent at the α-carbon atom of the acyl group.
