- Stereoselective synthesis of novel benzoins catalysed by benzaldehyde lyase in a gel-stabilised two-phase system
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Asymmetric benzoin condensation was performed using recombinant benzaldehyde lyase (BAL) from Pseudomonas fluorescens Biovar I. To enable the conversion of hydrophobic substrates, the enzyme was entrapped in polyvinyl alcohol and suspended in hexane. Compared to the reported application of the biocatalyst in an aqueous phase containing 20% DMSO, the productivity of the resulting gel-stabilised two-phase system was 3-fold better. The entrapment process had an efficiency of >90%, no enzyme or cofactor was lost during reaction or storage. The entrapped enzyme was stable in hexane for 1 week at 4°C and more than 1 month at -20°C. Without preceding optimisation the novel benzoins (R)-1,2-di(3-furanyl)-2-hydroxyethanone, (R)-2-hydroxy-1,2-di(3- thienyl) ethanone, (R)-1,2-di(4-ethoxyphenyl)-2-hydroxyethanone, (R)-1,2-di(3-ethoxyphenyl)-2-hydroxyethanone, (R)-2-hydroxy-1,2-di(3-tolyl) ethanone, and (R)-1,2-di(benzofuran-2-yl)-2-hydroxyethanone were prepared with yields up to 31.8% and enantiomeric excess >99%.
- Hischer, Tanja,Gocke, D?rte,Fernández, María,Hoyos, Pilar,Alcántara, Andrés R.,Sinisterra, José V.,Hartmeier, Winfried,Ansorge-Schumacher, Marion B.
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- Unexpected transformation of aldehydes into benzoins with Copper(I)/Samarium
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The reductive coupling of aldehydes to afford pinacolic alcohols using all kinds of reducing agents involving samarium is well known. In this report, however, treatment of aromatic aldehydes with Cu(I)/Sm system produces benoins and/or benzils in good yields. A possible mechanism is proposed where Cu(I) not only activates the Sm metal but also promotes the dehydrogenation of the intermediates, during which a Cu(III) species may be involved. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications for the following free supplemental resource(s): Full experimental and spectral details.]
- Liu, Yongjun,Wang, Hui,Fu, Yulong,Qi, Yan,Yang, Kuiwei
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p. 259 - 266
(2013/12/04)
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- Chiral cobalt-catalyzed enantiomer-differentiating oxidation of racemic benzoins by using molecular oxygen as stoichiometric oxidant
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A study was conducted to demonstrate chiral cobalt-catalyzed enantiomer-differentiating oxidation of racemic benzoins using molecular oxygen as stoichiometric oxidant. The cobalt-catalyzed asymmetric oxidation was performed with racemic benzoins due to th
- Alamsetti, Santosh Kumar,Muthupandi, Pandi,Sekar, Govindasamy
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supporting information; experimental part
p. 5424 - 5427
(2009/12/27)
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- Galactose oxidase model: Biomimetic enantiomer-differentiating oxidation of alcohols by a chiral copper complex
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An enantiopure analogue of galactose oxidase (GO) was synthesized from an easily and readily available source with a similar activity of GO's in primary alcohol oxidation and enantioselective catalysts for aerobic oxidative kinetic resolution (AORK) of racemic secondary alcohols. Enantiopure (R)-binam was treated with Cu(OTf)2 in toluene at room temperature for one hour to give a (R)-binam-Cu complex. It is found that enantiopure benzoin is an important intermediate in the synthesis of a potent anticancer agent and can been synthesized by enzymatic hydrolysis with benzaldehyde lyase (BAL). The S enantiomer of the racemate is oxidized faster to the corresponding benzil and the slow-reacting R enentiomer of benzoin is recovered in an enantiomerically enriched form. It is also observed that ortho substitution reduces the rate of reaction, while a reduced enentioselectivity is observed in case of ortho-substituted benzoin.
- Alamsetti, Santosh Kumar,Mannam, Sreedevi,Mutupandi, Pandi,Sekar, Govindasamy
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supporting information; experimental part
p. 1086 - 1090
(2009/10/23)
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- Triphenylamine-modified quinoxaline derivatives as two-photon photoinitiators
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Two new chromophores, triphenylamine-modified quinoxaline (TPAQ) and benzoquinoxaline (TPABQ), were synthesized, and their linear spectroscopy and two-photon absorption properties were investigated. For comparison, 4-ethoxyphenyl-substituted quinoxaline (EOQ) and benzoquinoxaline (EOBQ) were prepared. The results showed that TPAQ possesses a high fluorescence quantum yield and a high δ2PA value of >160 GM in the laser light wavelength range of 780-820 nm, and is superior to most common benzil-type compounds as a photoinitiator in two-photon initiated polymerization. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009.
- Cao, Xingbo,Jin, Feng,Li, Ying-Feng,Chen, Wei-Qiang,Duan, Xuan-Ming,Yang, Lian-Ming
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experimental part
p. 1578 - 1582
(2009/10/30)
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- Discotic liquid crystals of transition metal complexes, 31: Establishment of mesomorphism and thermochromism of bis[1,2-bis(4-n-alkoxyphenyl)ethane-1,2-dithiolene]nickel complexes
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Two series of bis[1,2-bis(4-n-alkylphenyl)ethane-1,2-dithiolene]nickel, Cn-Ni (n= 1-12), and bis[1,2-bis(4-n-alkoxyphenyl)ethane-1,2-dithiolene]nickel, CnO-Ni(n = 1-12, 14, 16, 18), have been synthesized. Their mesomorphism, thermochromism, supramolecular structures and π-acceptor property have been investigated by using different scanning calorimetry, polarizing microscopy, temperature-dependent X-ray diffraction technique, electronic spectroscopy and cyclic voltammetry. From the X-ray diffraction and electronic spectral results, it was established that the CnO-Ni complexes for n ≤ 10 exhibit two differently colored discotic lamellar (DL) mesophases whereas none of the Cn-Ni complexes has a mesophase, and that the thermochromism (brown→green) is attributable to a slow transformation from the Ni-Ni bonded dimers to the Ni-S bonded dimers.
- Horie,Takagi,Hasebe,Ozawa,Ohta
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p. 1063 - 1071
(2007/10/03)
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- Colour and Conformation of Some Derivatives of Benzil in the Solid State. Crystal Structures of 2,2'-Dimethoxy-, 4,4'-Dimethoxy-, 4,4'-Diethoxy- and 4,4'-Dibenzyloxy-benzil
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The crystal structures of the colourless 2,2'-dimethoxybenzil (2) and 4,4'-diethoxybenzil (6), the yellow 4,4'-dimethoxybenzil (5), and the yellow polymorph of 4,4'-dibenzyloxybenzil (7) have been determined by single-crystal X-ray studies from diffractom
- Cannon, Jack R.,Patrick, Vincent A.,White, Allan H.
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p. 1631 - 1646
(2007/10/02)
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- Preparation and antiinflammatory activity of some nonacidic trisubstituted imidazoles
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A number of trisubstituted imidazoles were made and several found to be potent antiinflammatory agents when examined in the carrageenan rat paw edema test. The antiinflammatory activity of these compounds is retained in adrenalectomized rats. Unlike many previously reported antiinflammatory agents, these compounds are extremely weak acids pK[a] ≥ 11) and are therefore not ionized at physiological pH. One compound, 4,5 bis (4 methoxyphenyl) 2 trifluoromethylimidazole (flumizole), is more potent than indometacin in the rat paw edema test and, in contrast to some related compounds, does not cause photosensitization in mice.
- Lombardino,Wiseman
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p. 1182 - 1188
(2007/10/04)
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