1072-86-2Relevant articles and documents
Asymmetric trans-dihydroxylation of cyclic olefins by enzymatic or chemo-enzymatic sequential epoxidation and hydrolysis in one-pot
Xu, Yi,Li, Aitao,Jia, Xin,Li, Zhi
, p. 2452 - 2458 (2011)
Novel and efficient one-pot enzymatic and chemo-enzymatic synthetic methods are developed for the asymmetric trans-dihydroxylations of cyclic olefins 1a and 1bvia sequential epoxidation and hydrolysis. The Novozym 435 -mediated epoxidation of cyclohexene 1a and subsequent hydrolysis of the intermediate cyclohexene oxide 2a with resting cells of Sphingomonas sp. HXN-200 in one-pot gave (1R,2R)-cyclohexane diol 3a in 84% ee and 95% conversion. trans-Dihydroxylation of N-benzyloxycarbonyl 3-pyrroline 1b with the same enzymatic system gave the corresponding (3R,4R)-N- benzyloxycarbonyl-3,4-dihydroxy-pyrrolidine 3b in 93% ee and 94% conversion. In the one-pot chemo-enzymatic system, epoxidation of N-benzyloxycarbonyl 3-pyrroline 1b by m-CPBA and subsequent hydrolysis of epoxide intermediate 2b with resting cells of Sphingomonas sp. HXN-200 gave the trans-diol (3R,4R)-3b in 92% ee and 94-97% conversion. While the trans-dihydroxylation of cyclohexene 1a to (1R,2R)-cyclohexane diol 3a is reported for the first time, the trans-dihydroxylation of N-benzyloxycarbonyl 3-pyrroline 1b to (3R,4R)-3b with such an enzymatic or chemo-enzymatic system afforded a much higher product concentration than the same reaction with the system using a microorganism containing the two necessary enzymes. The developed one-pot enzymatic and chemo-enzymatic systems for the asymmetric trans-dihydroxylation of olefins are new, easy to prepare, adjust and operate, are high yielding, complementary to Sharpless asymmetric dihydroxylation and particularly useful for the asymmetric synthesis of cyclic trans-diols.
Synthesis of titanium containing MCM-41 from industrial hexafluorosilicic acid as epoxidation catalyst
Liu, Tieliang,Jin, Fang,Wang, Xianqiao,Fan, Yangchun,Yuan, Ming
, p. 316 - 323 (2017)
The industrial by-product hexafluorosilicic acid was investigated as silicate source for titanium containing MCM-41 (Si/Ti–MCM-41) synthesis. An extended and detailed study, which includes the effects of several factors such as the state and content of Ti, surfactant/Si ratio and template removal technique on the physicochemical properties and catalytic activity of Si/Ti–MCM-41, is presented; The Si/Ti–MCM-41 was also characterized by powder X-ray diffraction, N2 adsorption-desorption, fourier transform infrared spectroscopy, ultraviolet-visible spectrophotometer, thermal gravimetric measurements, X-ray fluorescence and scanning electron microscopy. The results show that the specific surface area and pore volume of the molecular sieve reach 1040 m2 g?1 and 0.74 cm3 g?1 under the hydrothermal conditions of the Si/Ti mole ratio equal to 60, CTAB/Si mole ratio to 0.81, hydrothermal temperature at 343 K and time for 3 h. The catalytic performance shows that samples have higher activity and selectivity for cyclohexene epoxidation to produce cyclohexene oxide. With the reaction temperature 333 K and mole ratio of cyclohexene/tertiary butyl peroxide hydrogen equal to 1, the highest cyclohexene conversion and epoxide selectivity is 79.23% and 95%, respectively. The catalyst activity has not obvious change with two times recycles.
Enantioselective Ester Hydrolyses Employing Rhizopus nigricans. A Method of Preparing and Assigning the Absolute Stereochemistry of Cyclic Alcohols
Kasai, Masaji,Kawai, Ken-ichi,Imuta, Mitsuru,Ziffer, Herman
, p. 675 - 679 (1984)
The mold Rhizopus nigricans has been used to hydrolyze enantioselectively the acetates of several series of benzocycloalken-3-ols and 2-substituted cycloalkanols to yield chiral alcohols.The configurations of the alcohols formed were established.The absolute stereochemistries of 25 of the 26 alcohols obtained were found to conform to a generalization based on the effective sizes of substituents on the carbinol carbon.The relative sizes of substituents required for agreement were identical with those employed in Horeu's method of establishing the absolute stereochemistry of the same compounds.The use of these microbially mediated hydrolyses to assign the absolute stereochemistry of cyclic secondary alcohols is compared to Horeau's method and to the use of empirical relations between the absolute stereochemistry of an enantiomer and the order, relative to its antipode, in which it is eluted from a chiral (Pirkle) column.
Direct proline-catalyzed asymmetric α-aminoxylation of ketones
Hayashi, Yujiro,Yamaguchi, Junichiro,Sumiya, Tatsunobu,Shoji, Mitsuru
, p. 1112 - 1115 (2004)
Nitrosobenzene is the oxygen source in the direct catalytic enantioselective α-aminoxylation of ketones catalyzed by L-proline [Eq. (1)]. Versatile α-aminoxylated ketones are obtained in high yield and with excellent enantioselectivities.
Calix[8]arene as New Platform for Cobalt-Salen Complexes Immobilization and Use in Hydrolytic Kinetic Resolution of Epoxides
Abdellah, Ibrahim,Martini, Cyril,Dos Santos, Amandine,Dragoe, Diana,Guérineau, Vincent,Huc, Vincent,Schulz, Emmanuelle
, p. 4761 - 4767 (2018)
Eight cobalt-salen complexes have been covalently attached to a calix[8]arene platform through a flexible linker by a procedure employing Click chemistry. The corresponding well-defined catalyst proved its efficiency in the hydrolytic kinetic resolution (HKR) of various epoxides through an operative bimetallic cooperative activation, demonstrating highly enhanced activity when compared to its monomeric analogue. As an insoluble complex, this multisite cobalt-salen catalyst could be easily recovered and reused in successive catalytic runs. Products were isolated by a simple filtration with virtually no cobalt traces and without requiring a prior purification by flash chromatography.
Selective electrochemical reduction of cinnamyl ethers in the presence of other allylic C-O bonds
Solis-Oba, Aida,Hudlicky, Tomas,Koroniak, Lukasz,Frey, Dean
, p. 1241 - 1243 (2001)
Several conduritol derivatives protected as allyl and cinnamyl ethers were subjected to electrochemical reduction at a mercury cathode, resulting in selective removal of the cinnamyl group.
Two alternative routes for 1,2-cyclohexanediol synthesis by means of green processes: Cyclohexene dihydroxylation and catechol hydrogenation
Antonetti, Claudia,Galletti, Anna Maria Raspolli,Accorinti, Pasquale,Alini, Stefano,Babini, Pierpaolo,Raabova, Katerina,Rozhko, Elena,Caldarelli, Aurora,Righi, Paolo,Cavani, Fabrizio,Concepcion, Patricia
, p. 21 - 31 (2013)
In this paper we compare two different reactions, aimed at the synthesis of 1,2-cyclohexanediol. Specifically: (a) the direct epoxidation and hydrolysis (dihydroxylation) of cyclohexene to trans-1,2-cyclohexanediol, with an aqueous solution of hydrogen peroxide, and (b) the hydrogenation of catechol to a mixture of cis and trans-1,2-cyclohexanediol, in an attempt to establish green protocols for the synthesis of diols. Both reactions, the dihydroxylation of cyclohexene and the hydrogenation of catechol, were carried out without organic solvents. In the former case, an unprecedented 97.4% yield to the glycol was obtained, by selecting proper reaction conditions and using a tungstic acid/phosphoric acid catalyst, in a biphasic system with a phase-transfer agent. In the second approach, a heterogeneous alumina-supported Ru(OH)x catalyst was used, and a 90% yield to the glycol was obtained. A comparison of the two processes allowed to show the lower environmental impact of the catechol hydrogenation route.
Highly enantioselective hydrolysis of alicyclic meso-epoxides with a bacterial epoxide hydrolase from Sphingomonas sp. HXN-200: Simple syntheses of alicyclic vicinal trans-diols
Chang, Dongliang,Wang, Zunsheng,Heringa, Maarten F.,Wirthner, Renato,Witholt, Bernard,Li, Zhi
, p. 960 - 961 (2003)
Hydrolysis of N-benzyloxycarbonyl-3,4-epoxy-pyrrolidine and cyclohexene oxide with the epoxide hydrolase of Sphingomonas sp. HXN-200, respectively, gave the corresponding vicinal trans-diols in high ee and yield, representing the first example of enantioselective hydrolysis of a meso-epoxide with a bacterial epoxide hydrolase.
Comparing Different Strategies in Directed Evolution of Enzyme Stereoselectivity: Single- versus Double-Code Saturation Mutagenesis
Sun, Zhoutong,Lonsdale, Richard,Li, Guangyue,Reetz, Manfred T.
, p. 1865 - 1872 (2016)
Saturation mutagenesis at sites lining the binding pockets of enzymes constitutes a viable protein engineering technique for enhancing or inverting stereoselectivity. Statistical analysis shows that oversampling in the screening step (the bottleneck) increases astronomically as the number of residues in the randomization site increases, which is the reason why reduced amino acid alphabets have been employed, in addition to splitting large sites into smaller ones. Limonene epoxide hydrolase (LEH) has previously served as the experimental platform in these methodological efforts, enabling comparisons between single-code saturation mutagenesis (SCSM) and triple-code saturation mutagenesis (TCSM); these employ either only one or three amino acids, respectively, as building blocks. In this study the comparative platform is extended by exploring the efficacy of double-code saturation mutagenesis (DCSM), in which the reduced amino acid alphabet consists of two members, chosen according to the principles of rational design on the basis of structural information. The hydrolytic desymmetrization of cyclohexene oxide is used as the model reaction, with formation of either (R,R)- or (S,S)-cyclohexane-1,2-diol. DCSM proves to be clearly superior to the likewise tested SCSM, affording both R,R- and S,S-selective mutants. These variants are also good catalysts in reactions of further substrates. Docking computations reveal the basis of enantioselectivity.
Multiparameter Optimization in Directed Evolution: Engineering Thermostability, Enantioselectivity, and Activity of an Epoxide Hydrolase
Li, Guangyue,Zhang, Hui,Sun, Zhoutong,Liu, Xinqi,Reetz, Manfred T.
, p. 3679 - 3687 (2016)
The challenge of optimizing several parameters in the directed evolution of enzymes remains a central issue. In this study we address the thermostability, enantioselectivity, and activity of limonene epoxide hydrolase (LEH) as the catalyst in the hydrolytic desymmetrization of cyclohexene oxide with formation of (R,R)- and (S,S)-cyclohexane-1,2-diol. Wild type LEH shows a thermostability of T5030 = 41 °C and an enanioselectivity of 2% ee (S,S). Two approaches are described herein. In one strategy, the mutations generated previously by Janssen, Baker, and co-workers for notably increased thermostability are combined with mutations evolved earlier for enhanced enantioselectivity. Although highly enantioselective R,R and S,S variants (92-93% ee) with increases in T5030 by 10-11 °C were obtained, relative to wild type LEH the tradeoff in activity was significant. The second strategy based on the simultaneous optimization of both parameters using iterative saturation mutagenesis (ISM) with minimized tradeoff in activity proved to be superior. Several notably improved variants were observed, a reasonable "compromise" being R,R- and S,S-selective LEH variants (80-94% ee) showing enhanced thermostability by 5-10 °C and still reasonable levels of activity. Analysis of the X-ray structure of the S,S variant (94% ee) with and without diol product sheds light on the origin of altered stereoselectivity.
