35587-52-1Relevant academic research and scientific papers
Enantiocomplementary Epoxidation Reactions Catalyzed by an Engineered Cofactor-Independent Non-natural Peroxygenase
Crotti, Michele,Kataja, Kim M.,Poelarends, Gerrit J.,Saravanan, Thangavelu,Xu, Guangcai
, p. 10374 - 10378 (2020/04/23)
Peroxygenases are heme-dependent enzymes that use peroxide-borne oxygen to catalyze a wide range of oxyfunctionalization reactions. Herein, we report the engineering of an unusual cofactor-independent peroxygenase based on a promiscuous tautomerase that accepts different hydroperoxides (t-BuOOH and H2O2) to accomplish enantiocomplementary epoxidations of various α,β-unsaturated aldehydes (citral and substituted cinnamaldehydes), providing access to both enantiomers of the corresponding α,β-epoxy-aldehydes. High conversions (up to 98 %), high enantioselectivity (up to 98 % ee), and good product yields (50–80 %) were achieved. The reactions likely proceed via a reactive enzyme-bound iminium ion intermediate, allowing tweaking of the enzyme's activity and selectivity by protein engineering. Our results underscore the potential of catalytic promiscuity for the engineering of new cofactor-independent oxidative enzymes.
Gold-catalysed activation of epoxides: Application in the synthesis of bicyclic ketals
Balamurugan, Rengarajan,Kothapalli, Raveendra Babu,Thota, Ganesh Kumar
supporting information; experimental part, p. 1557 - 1569 (2011/04/25)
Gold-catalysed generation of diol equivalents from epoxides and their intramolecular reaction with Ca≡C bonds to generate bicyclic ketals is presented. This reaction essentially involves the formation of an acetonide, which subsequently cyclises on the alkyne intramolecularly under gold catalysis conditions. This method could be extended to make optically pure bicyclic ketals. Deuterium incorporation experiments were carried out to ascertain the mechanism of the reaction. Sequential activation of epoxide and alkyne moieties by a gold catalyst in acetone as solvent has been achieved. This strategyhas been employed to synthesise bicyclic ketals from epoxy alkynes. Copyright
Methods for protection of stratified squamous epithelium against injury by noxious substances and novel agents for use therefor
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, (2008/06/13)
Novel sulfate ester agents and the use of those agents for treating gastroesophageal reflux disease (GERD) are described, exemplary agents being of the formula: wherein X is —OCH2— or —CH2O—; Y is a group pendant from X comprising at least one —OSO3R4 moiety, wherein R4 is H or a pharmaceutically acceptable cation; n is an integer from 1-3; and R1 and R2 are each independently selected from the group consisting of —H, a halogen with an atomic number from 9 to 53, —SO3R4, —NCS, —NCO, —NH(CO)—OR3, —NH(CS)SR3, —NH(C═NH)OR3, —NHCOCH2Cl, —NHCOCH2Br, —NHCO—CH═CH2, —NHC(O)—CF3, wherein R4 is H or a pharmaceutically acceptable cation.
Mechanism of asymmetric epoxidation. 1. Kinetics
Woodard, Scott S.,Finn,Sharpless, K. Barry
, p. 106 - 113 (2007/10/02)
The rate of titanium-tartrate-catalyzed asymmetric epoxidation of allylic alcohols is shown to be first order in substrate and oxidant, and inverse second order in inhibitor alcohol, under pseudo-first-order conditions in catalyst. The rate is slowed by substitution of electron-withdrawing substituents on the olefin and varies slightly with solvent, CH2Cl2 being the solvent of choice. Asymmetric induction suffers when the size of the alkyl hydroperoxide is reduced. Kinetic resolution of secondary allylic alcohols is shown to be sensitive to the size of the tartrate ester group and insensitive to the steric nature of inhibitor alcohol. Most importantly, the species containing equimolar amounts of Ti and tartrate is shown to be the most active catalyst in the reaction mixture, mediating reaction at much faster rates than titanium tetraalkoxide alone.
