- Analyzing the hydrocyanation reaction: Chiral HPLC and the synthesis of racemic cyanohydrins
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A method to directly analyze unprotected cyanohydrins (with regard to enantiomeric purity and conversion) via chiral HPLC is described. The influence of the solvent composition on the stability of the unprotected cyanohydrins is investigated. By acidifying the solvent during HPLC analysis, hydrocyanation reactions can be directly followed in time. For many chiral cyanohydrins it is possible to determine both conversion and enantiomeric purity without prior protection of the cyanohydrin. Using a special aqueous-organic two-phase system racemic cyanohydrins can be synthesized in excellent yields.
- Jan Gerrits, Pieter,Zumbr?gel, Friedhelm,Marcus, Jan
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- Immobilized Baliospermum montanum hydroxynitrile lyase catalyzed synthesis of chiral cyanohydrins
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Hydroxynitrile lyase (HNL) catalyzed enantioselective C–C bond formation is an efficient approach to synthesize chiral cyanohydrins which are important building blocks in the synthesis of a number of fine chemicals, agrochemicals and pharmaceuticals. Immobilization of HNL is known to provide robustness, reusability and in some cases also enhances activity and selectivity. We optimized the preparation of immobilization of Baliospermium montanum HNL (BmHNL) by cross linking enzyme aggregate (CLEA) method and characterized it by SEM. Optimization of biocatalytic parameters was performed to obtain highest % conversion and ee of (S)-mandelonitrile from benzaldehyde using CLEA-BmHNL. The optimized reaction parameters were: 20 min of reaction time, 7 U of CLEA-BmHNL, 1.2 mM substrate, and 300 mM citrate buffer pH 4.2, that synthesized (S)-mandelonitrile in ~99% ee and ~60% conversion. Addition of organic solvent in CLEA-BmHNL biocatalysis did not improve in % ee or conversion of product unlike other CLEA-HNLs. CLEA-BmHNL could be successfully reused for eight consecutive cycles without loss of conversion or product formation and five cycles with a little loss in enantioselectivity. Eleven different chiral cyanohydrins were synthesized under optimal biocatalytic conditions in up to 99% ee and 59% conversion, however the % conversion and ee varied for different products. CLEA-BmHNL has improved the enantioselectivity of (S)-mandelonitrile synthesis compared to the use of purified BmHNL. Nine aldehydes not tested earlier with BmHNL were converted into their corresponding (S)-cyanohydrins for the first time using CLEA-BmHNL. Among the eleven (S)-cyanohydrins syntheses reported here, eight of them have not been synthesized by any CLEA-HNL. Overall, this study showed preparation, characterization of a stable, robust and recyclable biocatalyst i.e. CLEA-BmHNL and its biocatalytic application in the synthesis of different (S)-aromatic cyanohydrins.
- Jangir, Nisha,Padhi, Santosh Kumar
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- Fast microwave-assisted resolution of (±)-cyanohydrins promoted by lipase from Candida antarctica
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Enzymatic kinetic resolution (EKR) of (±)-cyanohydrins was performed by using immobilized lipase from Candida antarctica (CALB) under conventional ordinary conditions (orbital shaking) and under microwave radiation (MW). The use of microwave radiation contributed very expressively on the reduction of the reaction time from 24 to 2 h. Most importantly, high selectivity (up to 92percent eep) as well as conversion was achieved under MW radiation (50-56percent).
- Ribeiro, Sandra S.,Ferreira, Irlon M.,Lima, Jo?o P. F.,De Sousa, Bruno A.,Carmona, Rafaela C.,Santos, Alcindo A. Dos,Porto, André L. M.
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p. 1344 - 1350
(2015/07/15)
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- Application of crude preparations of leaves from food plants for the formation of cyanohydrins with high enantiomeric excesses
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Crude preparations obtained from mamey (Pouteria sapota), capulin (Prunus serotina var. capulli) and peach (Prunus persica) leaves were used to catalyze the enantioselective addition of HCN to a variety of aldehydes. The corresponding cyanohydrins were obtained with high levels of enantioselectivity, comparable with those obtained with other catalysts used for the same purpose.
- Hernandez, Liliana,Luna, Hector,Solis, Aida,Vazquez, Alfredo
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p. 2813 - 2816
(2007/10/03)
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- A new (R)-hydroxynitrile lyase from Prunus mume: Asymmetric synthesis of cyanohydrins
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A new hydroxynitrile lyase (HNL) was isolated from the seed of Japanese apricot (Prunus mume). The enzyme has similar properties with HNL isolated from other Prunus species and is FAD containing enzyme. It accepts a large number of unnatural substrates (benzaldehyde and its variant) for the addition of HCN to produce the corresponding cyanohydrins in excellent optical and chemical yields. A new HPLC based enantioselective assay technique was developed for the enzyme, which promotes the addition of KCN to benzaldehyde in a buffered solution (pH=4.5).
- Nanda, Samik,Kato, Yasuo,Asano, Yasuhisa
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p. 10908 - 10916
(2007/10/03)
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- Synthesis and antimicrobial activity of some heterocyclic compounds
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Condensation of 2-phenyl-3-(4-benzoyl hydride)-1,3-quinazolin-4(4H)-one (1) with various aldehydes gives 2-phenyl-3-(4-arylidene-benzoylhydrazide)-1,3-quinazolin-4(4H)-one (II), which on cycloaddition with mercaptoacetic acid yield 4-thiazolidinones (IIIa-o).Compound (I) on treatment with aromatic cyanohydrines and aryl isothiocyanates gives α-carbohydrazino nitriles of (IVa-m) and thiosemicarbazides (Va-l) respectively.The structures of III-V have been elucidated on the basis of their elemental analysis and spectral data.These compounds exhibit moderate to goodantibacterial and tuberculostatic activities.
- Trivedi, P. B.,Undavia, N. K.,Dave, A. M.,Bhatt, K. N.,Desai, N. C.
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p. 497 - 500
(2007/10/02)
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- Reductive Coupling of Benzoyl Cyanide and Carbonyl Compounds by Aqueous Ti(III) Ions. A New Convenient and Selective Access to the Less Stable Mixed Benzoins
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The reactive species formed by the Ti(III) ion reduction of benzoyl cyanide (1) adds to the C-atom of carbonyl compounds 2 under simple experimental conditions.The intermediate 1,2-diols 3 are smoothly converted, without isolation, into the less thermodynamically stable mixed benzoins 4, which are not accessible by the classical benzoin condensation.The possible mechanisms involved in the reaction are discussed.
- Clerici, Angelo,Porta, Ombretta
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p. 2889 - 2893
(2007/10/02)
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- Hydroxynitrile lyases from almond and sorghum as biocatalysts
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Hydroxynitrile lyases from sweet almond (E.C.4.1.2.10) and from sorghum biocolor (E.C.4.1.2.11) have been purified to homogeneity by ion-exchange chromatography.These enzymes catalyse the decomposition of α-hydroxynitriles to aldehydes and hydrocyanic acid (HCN) and show great promise for synthetic applications in the reverse reaction: the stereospecific addition of HCN to aldehydes to form enantio-pure α-hydroxynitriles.Physical and kinetic characteristics of the two dominating isoenzymes in each source were compared and revaled appreciable species-specific differences in substrate specificity between iso forms within one species, were, however, found to be small.The native molecular weight for the sorghum lyase was found to be 95kDa.This is in contrast with an earlier reported value of 180 kDa.From the kinetic parameters Km and Vmax, a specificity constant was calculated, which can be used to predict the potential application of oxynitrilase as a biocatalyst for specific synthetic purposes.
- Smitskamp-Wilms, E.,Brusse, J.,Gen, A. van der,Scharrenburg, G.J.M. van,Sloothaak, J. B.
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p. 209 - 215
(2007/10/02)
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