22584-00-5Relevant articles and documents
Chemoenzymatic asymmetric synthesis of pregabalin precursors via asymmetric bioreduction of β-cyanoacrylate esters using ene-reductases
Winkler, Christoph K.,Clay, Dorina,Davies, Simon,O'Neill, Pat,McDaid, Paul,Debarge, Sebastien,Steflik, Jeremy,Karmilowicz, Mike,Wong, John W.,Faber, Kurt
, p. 1525 - 1533 (2013/04/10)
The asymmetric bioreduction of a library of β-cyanoacrylate esters using ene-reductases was studied with the aim to provide a biocatalytic route to precursors for GABA analogues, such as pregabalin. The stereochemical outcome could be controlled by substrate-engineering through size-variation of the ester moiety and by employing stereochemically pure (E)- or (Z)-isomers, which allowed to access both enantiomers of each product in up to quantitative conversion in enantiomerically pure form. In addition, stereoselectivities and conversions could be improved by mutant variants of OPR1, and the utility of the system was demonstrated by preparative-scale applications.
Electrochemical Carbon-skeleton Rearrangements catalysed by Hydrophobic Vitamin B12 immobilised in a Polymer-coated Electrode
Murakami, Yukito,Hisaeda, Yoshio,Ozaki, Toshiaki,Matsuda, Yoshihisa
, p. 1094 - 1096 (2007/10/02)
A glassy carbon electrode was coated with a polymer species derived from a hydrophobic vitamin B12 and Araldite CT-200, and the immobilised cobalt complex catalysed the electrochemical carbon-skeleton rearrangements of alkyl halides having electron-withdrawing groups.
Redox Behavior of Simple Vitamin B12 Model Complexes and Electrochemical Catalysis of Carbon-Skeleton Rearrangements
Murakami, Yukito,Hisaeda, Yoshio,Fan, Sheng-Di,Matsuda, Yoshihisa
, p. 2219 - 2228 (2007/10/02)
Various cobalt complexes of 4,10-dipropyl-5,9-diazatrideca-4,9-diene-3,10-dione dioxime, (C2C3)(DOH)2pn, were prepared, and redox behavior of them was investigated by means of cyclic voltammetry; Co(II)/Co(I) redox potentials in the range of -0.69 through -0.7 V vs.Ag/AgCl.The monomethylated complex, which has a cobalt-carbon bond at one axial site of the nuclear cobalt, was disproportionated to the dimethylated complex, involving two cobalt-carbon bonds at both axial sites, and the CoI species by one-electron reduction.The dimethylated complex was inactive for electrochemical reduction, but transformed into the monomethylated complex via cleavage of a cobalt-carbon bond upon electrochemical oxidation.The electrolyses of 1-bromo-2,2-bis(ethoxycarbonyl)propane, 1-bromo-2-cyano-2-ethoxycarbonylpropane, and 2-acetyl-1-bromo-2-ethoxycarbonylpropane in the presence of IIIBr2> in N,N-dimethylformamide did not proceed in a divided cell at -2.0 vs.Ag/AgCl, since the corresponding dialkylated complexes, inactive for electrochemical reduction, were formed in the course of reaction.When imidazole was added to solutions for the electrolysis, the reaction proceeded efficiently by the trans effect arising from the coordinated axial base and the corresponding carbon-skeleton rearrangement products were obtained.On the other hand, the carbon-skeleton rearrangement proceeded in an undivided cell even in the absence of imidazole; the dialkylated complex was decomposed to give the monoalkylated complex and the reduction and rearrangement products by electrochemical ocxidation on the anode.
Redox Behavior of Simple Vitamin B12 Model Complexes with Cobalt-Carbon Bonds and Catalytic Carbon-Skeleton Rearrangements
Murakami, Yukito,Hisaeda, Yoshio,Fan, Sheng-Di,Matsuda, Yoshihisa
, p. 835 - 838 (2007/10/02)
The cobalt complex of 2,10-diethyl-3,9-dipropyl-1,4,8,11-tetraaazaundeca-1,3,8,10-tetraene-1,11-diol catalyzed electrolyses of alkyl halides with electron-withdrawing groups at the β-position to afford rearrangement products via oxidation of the corresponding dialkylated complexes as intermediates.
Electrochemical Carbon-Skeleton Rearrangements as Catalyzed by Cyano-Coordinated Hydrophobic Vitamin B12
Murakami, Yukito,Hisaeda, Yoshio,Ozaki, Toshiaki,Matsuda, Yoshihisa
, p. 469 - 472 (2007/10/02)
Electrochemical carbon-skeleton rearrangements catalyzed by heptamethyl cobyrinate perchlorate proceeded more efficiently upon coordination of the cyanide ion to the central cobalt atom, and such enhanced catalysis was orihinated from facilitated formatio
Hydrophobic Vitamin B12. Part 6. Carbon-skeleton Rearrangement via Formation of Host-Guest Complexes derived from an 'Octopus Azaparacyclophane and hydrophobic Vitamin B12 Derivatives: a Novel Holoenzyme Model System
Murakami, Yukito,Hisaeda, Yoshio,Kikuchi, Jun-ichi,Ohno, Teruhisa,Suzuki, Masashi,et al.
, p. 1237 - 1246 (2007/10/02)
The alkylation reactions of a hydrophobic vitamin B12 derivative with alkyl bromides in an 'octopus' azaparacyclophane having eight hydrocarbon chains have been investigated.Molecular discrimination has been shown to originate from electrostatic interaction between the octopus cyclophane and the alkyl bromides.Alkylation was enhanced by desolvation and proximity effects operating on the reacting species via formation of a ternary complex composed of the octopus cyclophane, the hydrophobic vitamin B12 derivative, and an alkyl halide.Carbon-skeleton rearrangement reactions of alkyl ligands bound to the hydrophobic vitamin B12 were found to be markedly favoured in the hydrophobic cavity provided by the octopus cyclophane, relative to the reactions in methanol and benzene, under anaerobic photolysis conditions at ordinary temperatures.The same reactions took place readily in solid benzene below 4 deg C under similar conditions.The central cobalt atom of the hydrophobic vitamin B12 participates in the rearrangement reaction via formation of a tight pair with an alkyl radical species.Non-enzymic rearrangement reactions have been shown here to proceed quite efficiently by employing a relevant apoenzyme model.
Hydrophobic Vitamin B12. V. Electrochemical Carbon-Skeleton Rearrangement as Catalyzed by Hydrophobic Vitamin B12: Reaction Mechanisms and Migratory Aptitude of Functional Groups
Murakami, Yukito,Hisaeda, Yoshio,Ozaki, Toshiaki,Tashiro, Takako,Ohno, Teruhisa,et al.
, p. 311 - 324 (2007/10/02)
The carbon-skeleton rearrangements as catalyzed by heptamethyl cobyrinate perchlorate, 1ester>ClO4, were investigated under electrochemical conditions.The controlled-potential electrolysis of 2,2-bis(ethoxycarbonyl)-1-bromopropane, which is considered to be a model substrate for methylmalonyl-CoA mutase, was catalyzed by 1ester>ClO4 in N,N-dimethylformamide to give the rearrangement product, 1,2-bis(ethoxycarbonyl)propane, as a major one at -1.5 V vs.SCE in the presence of acetic acid and at potentials more cathodic than -1.8 V vs.SCE without acetic acid in the dark.The electrochemical carbon-skeleton rearrangement was postulated to proceed via formation of anionic intermediates.The electrolyses of 1-bromo-2-cyano-2-ethoxycarbonylpropane, 2-acetyl-1-bromo-2-ethoxycarbonylpropane, and 1-bromo-2-propane with 1ester>ClO4 also afforded the corresponding carbon-skeleton rearrangement products.The results indicated that substrates with two electron-withdrawing groups placed on the β-carbon atom with combination of one carboxylic ester and one of carboxylic ester, acetyl, and cyano moieties readily gave the corresponding rearrangement products which were derived from individual migration of the substituent groups.Substrates with only one of the electron-withdrawing groups, carboxylic ester, acetyl, and cyano, did not give any rearrangement product, but a substrate with one thioester group afforded the corresponding rearrangement product.The migratory aptitude of electron-withdrawing groups was found to decrease in the order: COSR>COR>COOR>CN.Both electronic character and steric bulkiness of the migrating groups are apparently reflected on this tendency, even though relative contributions of these effects are much dependent on the nature of β-substituents.
Cyclization of cyanoalkyl radicals
Ogibin,Troyanskii,Nikishin
, p. 767 - 771 (2007/10/05)
Intramolecular homolytic addition to the CN group was observed for the first time. As the result of the reaction, and the subsequent hydrolysis of the cyclization product, cyanoalkyl radicals of type RCHXCN, where X is a chain of three carbon atoms and R is hydrogen or alkyl, are converted in aqueous solution into cycloalkanones[Figure not available: see fulltext.]. The cyanoalkyl radicals, in which X is a chain 4 or 5 C atoms, are partially converted to the corresponding cycloalkanones.
