67315-76-8Relevant academic research and scientific papers
Engineering the promiscuous racemase activity of an arylmalonate decarboxylase
Kourist, Robert,Miyauchi, Yusuke,Uemura, Daisuke,Miyamoto, Kenji
experimental part, p. 557 - 563 (2011/03/21)
Variant G74C of arylmalonate decarboxylase (AMDase) from Bordatella bronchoseptica has a unique racemising activity towards profens. By protein engineering, variant G74C/V43A with a 20-fold shift towards promiscuous racemisation was obtained, based on a reduced activity in the decarboxylation reaction and a two-fold increase in the racemisation activity. The mutant showed an extended substrate range, with a 30-fold increase in the reaction rate towards ketoprofen. Molecular dynamics simulations and the substrate profile of the racemase indicate that the steric and polar effects of the substrate structure play a more dominant role on catalysis than mere kinetic α-proton acidity. The observation that the conversion of β,γ-unsaturated carboxylic acids does not lead to a rearrangement to form their α,β isomers indicates a concerted rather than a stepwise mechanism. Interestingly, a substrate bearing a nitro group instead of the carboxylic acid group on the α-carbon atom was also converted by the racemase.
The dimethyldioxirane-mediated oxidation of phenylethyne
Zeller, Klaus-Peter,Kowallik, Meike,Haiss, Peter
, p. 2310 - 2318 (2007/10/03)
The product pattern found for the dimethyldioxirane-mediated oxidation of phenylethyne strongly depends on the reaction conditions. Dimethyldioxirane generated in situ from caroate (HSO5) and acetone in acetonitrile-water furnishes phenylacetic acid as the main product. With solutions of dimethyldioxirane in acetone, mandelic acid and phenylacetic acid are mainly formed. The relative abundances of the two acids depend on the residual water present in the dimethyldioxirane-acetone solution. Application of thoroughly dried solutions of the reagent effects increased formation of mandelic acid. When phenylethyne is oxidized by dimethyldioxirane transferred into tetrachloromethane, to minimize traces of water even further, oligomeric mandelic acid is obtained. The results are rationalized by the initial formation of phenyloxirene, which is known to equilibrate with phenylformylcarbene and bcnzoylcarbene. Subsequent Wolff rearrangement produces intermediate phenylketene, which can be trapped by water as phenylacetic acid or suffer from further oxidation to the α-lactone of mandelic acid. The α-lactone can either react with water to yield mandelic acid or, under anhydrous conditions, to yield oligomeric mandelic acid. In addition to mandelic acid and phenylacetic acid phenylglyoxylic acid, benzoic acid and benzaldehyde are observed as reaction products. The formation of phenylglyoxylic acid by transfer of two oxygen atoms to the in rear ranged carbon skeleton of phenylethyne followed by oxygen insertion into the aldehydic C-H bond of the intermediately formed phenylglyoxal is discussed. In a second pathway this acid is formed by partial oxidation of mandelic acid. Benzaldehyde and benzoic acid are explained as products of the oxidative degradation of the α-lactone by dimethyldioxirane. Under in situ conditions benzoic acid is also formed by caroate initiated oxidative decarboxylation of phenylglyoxylic acid and/or intermediate phenylglyoxal. The Royal Society of Chemistry 2005.
Kinetics and mechanism of hexachloroplatinate(IV) reduction by some neutralized α-hydroxy acids in a carbonate-hydrogencarbonate buffer medium
Pal, Biswajit,Sen Gupta, Kalyan Kali
, p. 553 - 560 (2007/10/03)
The kinetics of hexachloroplatinate(IV) reduction by some neutralized α-hydroxy acids such as glycolic, lactic, α-hydroxyisobutyric, mandelic, atrolactic, and benzilic acids in a carbonate-hydrogencarbonate buffer medium have been investigated. Platinum(IV) is reduced by the substrates to platinum(II) in a one-step two-electron process, whereas the substrates are oxidized to give formaldehyde, acetaldehyde, acetone, benzaldehyde, acetophenone, and benzophenone for the respective reactions. The pseudo- first-order rate constant is independent of the initial [platinum(IV)] as well as [OH-]. The reaction rate increases with increasing [substrate], but decreases with increasing chloride concentration. The reactions obey the following rate expression: -d[Pt(IV)](t)dr=kK(e)[A-][Pt(IV)]t/Cl-]+K(e)A- ]. The reactions proceed through an initial 1: 1 complex formation between the reactants, followed by decomposition of the complex to give the respective reaction products via C-C bond cleavage. The reactivity of the α- hydroxycarboxylate towards Pt(IV) are as follows: atrolactic acid > mandelic acid > benzilic acid > α-hydroxyisobutyric acid > lactic acid > glycolic acid. Thermodynamic parameters for the decomposition step have been evaluated. The mechanism of the reactions is discussed.
Biosynthetic Studies of ω-Cycloheptyl Fatty Acids in Alicyclobacillus cycloheptanicus. Formation of Cycloheptanecarboxylic Acid from Phenylacetic Acid
Moore, Bradley S.,Walker, Kevin,Tornus, Ingo,Handa, Sandeep,Poralla, Karl,Floss, Heinz G.
, p. 2173 - 2185 (2007/10/03)
The formation of the structurally novel, mono-substituted cycloheptane ring in ω-cycloheptyl fatty acids in Alicyclobacillus cycloheptanicus (formerly Bacillus cycloheptanicus) has been examined. Feeding experiments with 13C- and 2H-labeled intermediates demonstrated that cycloheptanecarboxylic acid (3), probably as its CoA thioester, is the starter unit for ω-cycloheptyl fatty acid biosynthesis. Analysis of the resultant labeling pattern from a feeding experiment with [U-13C6]-glucose suggested a shikimate pathway origin of 3 via aromatic amino acids. [1,2-13C2]Phenylacetic acid (6) was efficiently metabolized into the 3-derived moiety in a manner reminiscent of the seven-membered ring Pseudomonas metabolite thiotropocin. The fates of the aromatic and benzylic hydrogens of 6 were determined; these dictated various boundary conditions for the biosynthetic pathway from 6 to 3. Taken together with the results from feeding experiments with postulated cycloheptenylcarboxylate biosynthetic intermediates, the data lead us to propose a pathway which involves an oxidative ring-expansion of 6 to a hydroxynorcaradiene intermediate followed by a series of double bond reductions and dehydrations to the saturated 3.
Reduction of manganate(VI) by mandelic acid and its significance to development of a general mechanism for oxidation of organic compounds by high-valent transition metal oxides
Lee, Donald G.,Chen, Tao
, p. 11231 - 11236 (2007/10/02)
Results obtained from a study of the oxidation of mandelic acid and cyclobutanol by manganate(VI) indicate that reaction mechanisms traditionally applied to oxidations of this type (i.e., hydrogen atom or hydride ion transfers) may not be correct. Instead it appears that the reaction may be initiated by a 2 + 2 addition of the α-C-H bond to a manganese oxo double bond. This interpretation may be useful in the development of a general mechanism for the oxidation of organic compounds by high-valent transition metal oxides including more common oxidants such as permanganate, ruthenium tetroxide, and chromic acid.
The Oxidation of Alcohols by Permanganate. A Comparison with Other High-Valent Transition-Metal Oxidants
Lee, Donald G.,Chen, Tao
, p. 5341 - 5345 (2007/10/02)
The results obtained from a study of the oxidation of mandelic acid and cyclobutanol by permanganate in 1.0 M KOH are best accomodated by a mechanism in which the initial reaction is the addition of a manganese-oxo bond to the α-C-H bond of the alcohol, followed by homolytic cleavage of the resulting Mn-C bond to give free-radical intermediates.A comparison with other high-valent transition-metal oxidants suggests that it is possible to systematically classify the way in which these reagents react with alcohols on the basis of the initial reaction (C-H or O-H addition) and the cleavage mode of the metal-oxygen or metal-carbon bond (homolytic or heterolytic).The approach provides a framework for understanding these reactions that is less chaotic than the current situation where distinctive mechanisms have been proposed for each individual oxidant.
Mechanism of Oxidative Decarboxylation of Substituted Mandelic Acids by Alkaline Sodium Hypochlorite
Eliason, Robert,Platz, Jeffery,Carlsen, Per H. J.
, p. 491 - 493 (2007/10/02)
The mechanism of oxidative decarboxylation of 2-hydroxy-2-phenylethanoic acid (mandelic acid) by aqueous alkaline sodium hypochlorite (comercial bleach) has been studied.Kinetic studies for a series of 4-substituted mandelic acids (CH3O, CH3, H, F, Cl, CF
Vibrational Circular Dichroism of Phenylcarbinols. A Configurational Correlation
Polavarapu, Prasad L.,Fontana, Luca P.,Smith, Howard E.
, p. 94 - 99 (2007/10/02)
The vibrational circular dichroism (VCD) spectra of enantiomers of phenylcarbaniols were studied in the 1600-800 cm-1 region.In these molecules, the PhC(OH)H group is a common structural feature, and the chirality of this probe group correlates with the sign of a VCD band at about 1200 cm-1.Viewing the probe group with the fourth ligand behind it, a clockwise arrangement of the probe group substituents (with the usual sequence rule priority, OH > Ph > H), designated as a clockwise probe group chirality, results in a negative sign for the VCD band at about 1200 cm-1.For a counterclockwise probe group chirality, the VCD band is positive.On the basis of infrared and Raman spectral observations with deuterated analogues, this band is assigned to a *C-H deformation mode of the phenylcarbinols.
