cas 97070-79-6, (R)-(+)-4-CHLOROMANDELONITRILE

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Combining Photo-Organo Redox- and Enzyme Catalysis Facilitates Asymmetric C-H Bond Functionalization
In this study, we combined photo-organo redox catalysis and biocatalysis to achieve asymmetric C–H bond functionalization of simple alkane starting materials. The photo-organo catalyst anthraquinone sulfate (SAS) was employed to oxyfunctionalise alkanes to aldehydes and ketones. We coupled this light-driven reaction with asymmetric enzymatic functionalisations to yield chiral hydroxynitriles, amines, acyloins and α-chiral ketones with up to 99 % ee. In addition, we demonstrate functional group interconversion to alcohols, esters and carboxylic acids. The transformations can be performed as concurrent tandem reactions. We identified the degradation of substrates and inhibition of the biocatalysts as limiting factors affecting compatibility, due to reactive oxygen species generated in the photocatalytic step. These incompatibilities were addressed by reaction engineering, such as applying a two-phase system or temporal and spatial separation of the catalysts. Using a selection of eleven starting alkanes, one photo-organo catalyst and 8 diverse biocatalysts, we synthesized 26 products and report for the model compounds benzoin and mandelonitrile > 97 % ee at gram scale.
Zhang, Wuyuan,Fueyo, Elena Fernandez,Hollmann, Frank,Martin, Laura Leemans,Pesic, Milja,Wardenga, Rainer,H?hne, Matthias,Schmidt, Sandy
supporting information
p. 80 - 84
(2019/01/04)

Supported Ionic Liquid-Like Phases (SILLPs) as Immobilised Catalysts for the Multistep and Multicatalytic Continuous Flow Synthesis of Chiral Cyanohydrins
Supported Ionic Liquid-Like Phases have been found to be efficient organocatalysts for the synthesis of cyanohydrin esters under solvent-free conditions by an “electrophile-nucleophile dual activation” based on hydrogen bond formation. The combination of
Peris, Edgar,Porcar, Raúl,Burguete, María Isabel,García-Verdugo, Eduardo,Luis, Santiago V.
p. 1955 - 1962
(2019/03/13)

Preparation of chitosan-supported urea materials and their application in some organocatalytic procedures
An efficient and mild procedure was developed for the preparation of three chitosan-supported ureas containing electron-withdrawing groups. These catalysts were characterized and employed as organocatalysts in different transformations, including the enan
de Gonzalo, Gonzalo,Franconetti, Antonio,Fernández, Rosario,Lassaletta, José M.,Cabrera-Escribano, Francisca
p. 365 - 374
(2018/07/25)

High-Throughput Preparation of Optically Active Cyanohydrins Mediated by Lipases
Cyanohydrins are versatile compounds with high applicability in organic synthesis; they are used as starting materials for the synthesis of other chemical targets with high industrial added value. Lipase-mediated kinetic resolution reactions are a promising route for the synthesis of optically active cyanohydrins. These reactions can be carried out through the acylation of cyanohydrins or the deacylation of cyanohydrin esters, with different biocatalysts and under different reaction conditions. Unfortunately, depending on the substrate structure, long reaction times can be required to achieve suitable enantiomeric excesses. In this context, we present a high-throughput protocol for the production of optically active cyanohydrins in continuous-flow mode. The products were obtained with moderate to good enantioselectivity (E values from 8 up to >200) and with productivity values from 2.4 to 8.7 times higher in continuous-flow mode than in batch mode. Moreover, the reaction times were reduced from hours in batch mode to minutes in continuous-flow mode.
Thomas, Juliana Christina,Aggio, Bruno Bernardi,Marques de Oliveira, Alfredo Ricardo,Piovan, Leandro
p. 5964 - 5970
(2016/12/26)

Enantioselective cyanosilylation of aldehydes catalyzed by a multistereogenic salen-Mn(III) complex with a rotatable benzylic group as a helping hand
A multistereogenic salen-Mn(iii) complex bearing an aromatic pocket and two benzylic groups as helping hands was found to be efficient in the catalysis of asymmetric cyanosilylation. The salen-Mn catalyst partially mimics the functions of biocatalysts by
Wei, Yun-Long,Huang, Wei-Sheng,Cui, Yu-Ming,Yang, Ke-Fang,Xu, Zheng,Xu, Li-Wen
p. 3098 - 3103
(2015/02/02)

Fast microwave-assisted resolution of (±)-cyanohydrins promoted by lipase from Candida antarctica
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.
p. 1344 - 1350
(2015/07/15)

Design of nitrilases with superior activity and enantioselectivity towards sterically hindered nitrile by protein engineering
Abstract The enantioselective hydrolysis of ortho-chloromandelonitrile with nitrilase is one of the most attractive approaches to prepare (R)-ortho-chloromandelic acid. To date, efforts to develop this nitrilase-mediated process were plagued by either insufficient eep (enantiomeric excess of product) or low activity due to the steric hindrance from the ortho-substituted substrate. To improve the nitrilase potential for producing (R)-ortho-chloromandelic acid, an enhancement of both activity and enantioselectivity towards sterically hindered nitriles would be highly desirable. Molecular docking of the (R)-ortho-chloromandelonitrile into the active site of wild-type 2A6 nitrilase (nitA) allowed the identification of proximal nitA active site residues. Several residues (52, 132, 189 and 190) were selected as targets for single and double point mutation to improve nitA activity and enantioselectivity towards ortho-chloromandelonitrile. Targeted mutagenesis yielded several nitA variants with superior activity and enantioselectivity. The best mutant T132A/F189T exhibited a 4.37-fold higher specific activity (7.39 U/mg) towards ortho-chloromandelonitrile than the wild-type nitA. More importantly, the enantioselectivity (E) was improved from 17.34 to >200, resulting in a highly enantiopure product. Molecular docking experiments further support the enhanced activity and enantioselectivity shown experimentally and the structural effects of this amino acid substitution on the active site of nitA are provided. The amino acids at sites 189 and 132 determine the activity and enantioselectivity towards ortho-chloromandelonitrile. With mutant T132A/F189T as a catalyst, a maximum of 450 mM of (R)-ortho-chloromandelic acid was produced with a 90% conversion and >99% eep within 3 h. This is the first time that a high productivity of (R)-ortho-chloromandelic acid of up to 671.76 g L-1d-1 using a nitrilase-mediated approach is reported. The engineered T132A/F189T variant represents a promising and competitive biocatalyst for practical application in synthesizing (R)-ortho-chloromandelic acid.
Xue, Ya-Ping,Shi, Cheng-Ci,Xu, Zhe,Jiao, Biao,Liu, Zhi-Qiang,Huang, Jian-Feng,Zheng, Yu-Guo,Shen, Yin-Chu
p. 1741 - 1750
(2015/06/02)

Solid phase behavior in the chiral systems of various 2-hydroxy-2-phenylacetic acid (mandelic acid) derivatives
The solid phase behavior of a series of monosubstituted F-, Cl-, Br-, I-, and CH3- and two 2,4-halogen-disubstituted 2-hydroxy-2-phenylacetic acid (mandelic acid) derivatives was investigated. The study includes detailed information about melting temperature, melting enthalpy, X-ray diffraction data, as well as selected binary phase diagrams of the respective chiral systems. Aside from the known metastable conglomerate 2-chloromandelic acid, evidence for two more metastable conglomerates was found.
Von Langermann, Jan,Temmel, Erik,Seidel-Morgenstern, Andreas,Lorenz, Heike
p. 721 - 728
(2015/03/30)

Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes
Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino- 1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes
B?ocka, Ewelina,Bosiak, Mariusz J.,We?niak, Miros?aw,Ludwiczak, Agnieszka,Wojtczak, Andrzej
p. 554 - 562
(2014/05/06)

A simple separation method for (S)-hydroxynitrile lyase from cassava and its application in asymmetric cyanohydrination
Using an acetone precipitation method, crude (S)-hydroxynitrile lyase [(S)-MeHNL] was separated from Munihot esculenta (cassava) leaves, and used directly as biocatalyst to catalyze asymmetric cyanohydrination and produce cyanohydrins with enantiomeric purities (≥90% ee) significantly greater than those previously reported. The use of a water/i-Pr2O system with an enzyme, NaCN, and appropriate amounts of acetic acid is crucial in improving the stereoselectivity of cyanohydrin formation by minimizing the non-enzymatic reaction and the racemization of the chiral products. The proposed isolation method for crude (S)-MeHNL has a high value because of its simplicity, and low cost as well as the high activity of the crude (S)-MeHNL.
Zheng, Zubiao,Zi, Yan,Li, Zhongzhou,Zou, Xinzhuo
p. 434 - 439
(2013/06/27)

A novel bifunctional Ti(IV) complex catalyzed asymmetric silylcyanation of aldehydes
A novel Lewis acid and Lewis base bifunctional Ti(IV) complex was formed in situ upon the treatment of ligand (R)-3,3′-bis(diphenylphosphinoyl)-BINOL with Ti(PrO-i)4, which is proven to be an efficient catalyst in the asymmetric trimethylsilylc
Tang, Hongying,Zhang, Zhongbiao
experimental part
p. 31 - 35
(2011/10/09)

Unsymmetric salen ligands bearing a Lewis base: Intramolecularly cooperative catalysis for cyanosilylation of aldehydes
A series of unsymmetric salen ligands derived from 1,2-diaminocyclohexane bearing an appended Lewis base on the three-position of one aromatic ring were synthesized by the reaction of various functional salicyaldehydes with the condensation product of 1,2-diaminocyclohexane mono(hydrogen chloride) and 3,5-di-tert-butylsalicylaldehyde. These ligands in conjunction with Ti(O iPr)4 exhibited excellent activity in catalyzing the cyanosilylation of aldehydes with trimethylsilyl cyanide (TMSCN) at mild conditions. The highest activity was observed in the catalyst system with regard to the salen ligand bearing a diethylamino group, which proved to be active even at a high [aldehyde]/[catalyst] ratio up to 50000. In a low catalyst loading of 0.05 mol%, the quantitative conversion of benzaldehyde to the corresponding cyanosilylation product was found within 10 min. at ambient temperature. An intramolecularly cooperative catalysis was proposed wherein the central metal Ti(iv) is suggested to play a role of Lewis acid to activate aldehydes while the appended Lewis base to activate TMSCN.
Wen, Ye-Qian,Ren, Wei-Min,Lu, Xiao-Bing
supporting information; experimental part
p. 6323 - 6330
(2011/10/09)

Enantioselective silylcyanation of aldehydes catalyzed by new chiral oxovanadium complex
Oxovanadium(V) complex 4 was prepared from VOSO4 and tridentate Schiff base ligand, which was prepared from substituted salicylaldehyde and inexpensive (S)-valine. Asymmetric silylcyanation of the aldehydes catalyzed by catalyst 4 afforded cyanohydrins with good enantioselectivities.
Chu, Chang-Ying,Hsu, Chu-Tin,Lo, Po Hsiang,Uang, Biing-Jiun
scheme or table
p. 1981 - 1984
(2012/03/10)

Preparation and reactions of optically active cyanohydrins derived from 4-chlorobenzaldehyde, cyclohexanone and 2-methylcyclohexanone using the (R) hydroxynitrile lyase from Prunus amygdalus
CYANURATION of 4-chlorobenzaldehyde (1), cyclohexanone (2a) and 2-methylcyclo-hexanone (2b) yielded the racemic 2-hydroxy-2-(4-chlorophenyl) ethanenitrile (R,S)-3, cyclohexanone cyanohydrin 21a and (R,S)-2- methylcyclohexanone cyanohydrin (R,S)-21b. The same reaction can be completed by using acetone cyanohydrin (4) as a transcyanating agent. The optically active cyanohydrins (R)-3 and (R)-21b could be respectively obtained by hydrocyanation of 1 and 2b using (R)-hydroxynitrile lyase (R) PaHNL [EC 4.1.2.10] from almonds (Prunus amygdalus) as a chiral catalyst. Cyanohydrins 3 and 21 in their racemic and optically active forms undergo a number of transformations which involve either the hydroxyl group or the cyanide function. Moreover, derivatization of 3 and 21b with (S)-Naproxen chloride (S)-7 gave the respective diastereoisomers 8 and 22b. The optical activities of (R)-3 and 21b as well as their derivatives were recorded. The postulated structures of the new products were supported with compatible elementary and spectroscopic (IR, 1H NMR, 13C NMR, MS and X-ray crystallography) analyses. The antitumor activity of some selected racemic new products and their respective optically active analogues were undertaken. The structure-activity relationship (SAR) was also discussed.
Yosef,Elmasry,Ismael, Eman H. I.,Mahran
p. 745 - 755
(2013/05/21)

Enzymatic kinetic resolution of racemic cyanohydrins via enantioselective acylation
Enzymatic kinetic resolution of a series of aromatic and aliphatic cyanohydrins in organic media has been investigated. The behavior of potential lipases, molecular sieves, acyl reagent, reaction temperature, and organic solvents on the kinetic resolution was studied. The influence of substrate structure, steric, and electronic nature and position of the aryl substituent on the enantioselectivity was discussed. Under the optimized reaction conditions, good enantioselectivity could be achieved for most of the investigated compounds. Specifically, substrates 1a, 1c, 1d, 1f, 1u could be resolved with the kinetic enantiomer ratio (E) higher than 200.
Xu, Qing,Xie, Yongli,Geng, Xiaohong,Chen, Peiran
experimental part
p. 624 - 630
(2010/09/07)

Room-temperature synthesis of enantioenriched non-protected cyanohydrins using vanadium(salalen) catalyst
Room-temperature synthesis of enantioenriched non-protected cyanohydrins using acetone cyanohydrin as the cyanide source was achieved by V(salalen) catalyst. Aliphatic aldehydes underwent the cyanation with 89-95% ee in the presence of only 0.2-0.4 mol% catalyst. Aromatic cyanohydrins were also obtained in high enantiomeric excesses under modified conditions.
Sakai, Yoshifumi,Mitote, Junko,Matsumoto, Kazuhiro,Katsuki, Tsutomu
supporting information; experimental part
p. 5787 - 5789
(2010/09/05)

Investigation of lewis acid versus lewis base catalysis in asymmetric cyanohydrin synthesis
The asymmetric addition of trimethylsilyl cyanide to aldehydes can be catalysed by Lewis acids and/or Lewis bases, which activate the aldehyde and trimethylsilyl cyanide, respectively. It is not always apparent from the structure of the catalyst whether Lewis acid or Lewis base catalysis predominates. To investigate this in the context of using salen complexes of titanium, vanadium and aluminium as catalysts, a Hammett analysis of asymmetric cyanohydrin synthesis was undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewis base catalysis give much smaller reaction constants. [{Ti(salen)O}2] was found to show the highest degree of Lewis acid catalysis, whereas two [VO(salen)X] (X = EtOSO3 or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions catalysed by [{Al(salen)}2O] and triphenyl- phosphine oxide, a non-linear Ham- mett plot was observed, which is indicative of a change in mechanism with increasing Lewis base catalysis as the carbonyl compound becomes more electron-deficient. These results suggested that the aluminium complex/tri- phenylphosphine oxide catalyst system should also catalyse the asymmetric addition of trimethylsilyl cyanide to ke- tones and this was found to be the case.
North, Michael,Omedes-Pujol, Marta,Williamson, Courtney
experimental part
p. 11367 - 11375
(2010/11/17)

Asymmetric synthesis of a new salen type-titanium complex as the catalyst for asymmetric trimethylsilylcyanation of aldehydes
This work describes the asymmetric synthesis of a new salen-type ligand via a Diels-Alder reaction and Curtius rearrangement. The ligand with a norbornane skeleton was used in the trimethylsilylcyanation of aldehydes, but the enantioselectivity was 55%ee. The norborane skeleton was cleaved to destroy this rigidity, and the eanatioselectivity was thereby increased to 85%ee.
Lin, Zheng-Chang,Chen, Chinpiao
experimental part
p. 726 - 737
(2011/04/23)

Asymmetric cyanohydrin formation from aldehydes catalyzed by manganese Schiff base complexes
The catalyst generated in situ from Mn(OAc)2 and a chiral Schiff base ligand exhibited excellent catalytic abilities in asymmetric cyanohydrin formation from aldehydes with sodium cyanide in up to 99% enantioselectivity and good yield.
Qu, Yanyang,Jing, Linhai,Wu, Zhiqing,Wu, Di,Zhou, Xiangge
experimental part
p. 187 - 190
(2010/04/28)

[Ru(phgly)2(binap)]/Li2CO3: A Highly Active, Robust, and Enantioselective Catalyst for the Cyanosilylation of Aldehydes
The right combination: A series of aromatic, heteroaromatic, aliphatic, and α,β-unsaturated aldehydes can be converted into the desired silylated cyanohydrins by reaction with (CH3)3SiCN and a catalyst system consisting of the combination of a chiral ruthenium complex and Li2CO3 (see scheme). The reaction is highly enantioselective and affords the R products with up to 98% ee within 24 h at a substrate-tocatalyst ratio of 10000:1. (Chemical Equation Presented).
Kurono, Nobuhito,Arai, Kenta,Uemura, Masato,Ohkuma, Takeshi
supporting information; experimental part
p. 6643 - 6646
(2009/03/12)

A new strategy for designing non-C2-symmetric monometallic bifunctional catalysts and their application in enantioselective cyanation of aldehydes
A monometallic bifunctional catalyst, in which only one imidazolyl moiety is directly attached at the 3-position of a binaphthol moiety, has been developed. The ligand (R)-1, which lacks C2-symmetry and flexible linkers, in combination with Ti(OiPr)4, has been demonstrated to promote the enantioselective cyanation of aldehydes with trimethylsilylcyanide (TMSCN), giving excellent enantioselectivities of up to 98 % ee and high yields of up to 99%. The use of this bifunctional catalytic system obviates the need for additives and is extremely simple as the reagents are added in one portion at the beginning of the reaction. The protocol has been found to tolerate a relatively wide range of aldehydes when 10 mol% of the (R)-1/Ti(OiPr) 4 complex is deployed in CH2Cl2 at -40°C, the conditions which proved most practical and effective. The asymmetric cyanations also proceeded with lower catalyst loadings (5 mol%, or even 2 mol%), still giving satisfactory enantiomeric excesses and yields. Interestingly, the use of freshly distilled TMSCN dried over CaH2 gave a low enantioselectivity and only a moderate yield of the adduct as compared with direct use of the commercial reagent. The results of 13C NMR spectroscopic studies implicate HCN as the actual reactive nucleophile.
Yang, Fei,Wei, Siping,Chen, Chien-An,Xi, Peihua,Yang, Li,Lan, Jingbo,Gau, Han-Mou,You, Jingsong
supporting information; experimental part
p. 2223 - 2231
(2009/04/06)

A novel chiral (salen)AlIII complex catalyzed asymmetric cyanosilylation of aldehydes
A novel chiral (salen)AlIII complex was synthesized through the reaction of Et2AlCl and salen (R,R)-1 derived from (R,R)-11,12-diamino-9,10-dihydro-9,10-ethanoanthracene. This complex is an efficient catalyst for the asymmetric trimethylsilylcyanation of aldehydes in the presence of tributylphosphane oxide as an additive. The use of 1 mol-% of the complex led to the corresponding cyanohydrins in high yields (85-94%) with good-to-excellent enantioselectivities (42-92%ee). Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Zeng, Zebing,Zhao, Guofeng,Zhou, Zhenghong,Tang, Chuchi
experimental part
p. 1615 - 1618
(2009/04/11)

An R-selective hydroxynitrile lyase from Arabidopsis thaliana with an α/β-hydrolase fold
Folding and selectivity: The noncyanogenic plant Arabidopsis thaliana contains a new hydroxynitrile lyase, which was cloned and characterized. This enzyme is readily available form a recombinant source, has a broad range of substrates, and enantioselectively transforms aliphatic and aromatic aldehydes as well as ketones into the corresponding R-cyanohydrins. (Chemical Equation Presented).
Andexer, Jennifer,Von Langermann, Jan,Mell, Annett,Bocola, Marco,Kragl, Udo,Eggert, Thorsten,Pohl, Martina
p. 8679 - 8681
(2008/09/18)

Enantioselective cyanosilylation of aldehydes catalyzed by a novel N,N′-dioxide-Ti(OiPr)4 bifunctional catalyst
A novel bifunctional asymmetric catalyst containing N-oxide and titanium(IV) was developed and applied to the asymmetric cyanosilylation of aldehydes. Optically active trimethylsilyl cyanohydrin ethers were obtained up to 99% yield and 80% ee in the presence of 5 mol % catalyst loading at -78 °C. Based on the experimental results, the catalytic cycle was proposed as a pathway in which Lewis acid and Lewis base activated aldehyde and trimethylsilylcyanide (TMSCN), respectively.
Zeng, Baiqing,Zhou, Xin,Liu, Xiaohua,Feng, Xiaoming
p. 5129 - 5136
(2008/02/01)

Enantioselective cyanosilylation of aldehydes catalysed by a diastereomeric mixture of atropisomeric thioureas
New bifunctional atropisomeric thioureas 1 were synthesised and tested as both a mixture of diastereomers (aR/aS)-(R,R)-1 and as single diastereomers (aR)-(R,R)-1 and (aR)-(S,S)-1, in the organocatalysed, enantioselective, cyanosilylation of a range of al
Steele, Rebecca M.,Monti, Chiara,Gennari, Cesare,Piarulli, Umberto,Andreoli, Federico,Vanthuyne, Nicolas,Roussel, Christian
p. 999 - 1006
(2007/10/03)

Asymmetric addition of trimethylsilyl cyanide to aldehydes promoted by chiral polymeric vanadium(V) salen complex as an efficient and recyclable catalyst
The asymmetric addition of trimethylsilyl cyanide to various aldehydes catalyzed by efficient new vanadyl polymeric salen complexes having 12 repeating salen units was investigated at room temperature. An excellent yield of the trimethylsilylether of cyanohydrins (up to 98%) with high chiral induction (96%) in case of 2-methylbenzaldehyde was achieved in 18 h. The catalyst recovered four times with retention of its performance.
Khan, Noor-ul H.,Agrawal, Santosh,Kureshy, Rukhsana I.,Abdi, Sayed H.R.,Mayani, Vishal J.,Jasra, Raksh V.
p. 2659 - 2666
(2007/10/03)

Asymmetric cyanohydrin synthesis catalyzed by Mn(salen) complex/triphenylphosphine oxide
Various aldehydes undergo enantioselective silylcyanation with (CH 3)3SiCN trimethylsilylcyanation (TMSCN) employing chiral Mn(salen) and achiral POPh3 as the catalysts. This is the double activation where Mn(salen) plays
Kim, Sung Soo,Lee, Sang Hyuck
p. 751 - 759
(2007/10/03)

Asymmetric cyanohydrin synthesis catalyzed by Al(salen)/triphenylphosphane oxide
Various aldehydes undergo asymmetric trimethylsilylcyanation with (CH 3)3SiCN (TMSCN) in the presence of a chiral Al(salen) complex and Ph3PO as the catalyst. This is a double activation where Al(salen) plays the role of Lewis acd and POPh3 acts as a Lewis base. Various kind of aldehydes were subjected to the enantioselective addition of (CH3)3SiCN at temperatures between -40 °C and -50 °C. Hydrolysis of the adducts gave cyanohydrins with over 90 % yield and 80 % ee in most cases. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
Kim, Sung Soo,Song, Dae Ho
p. 1777 - 1780
(2007/10/03)

A new (R)-hydroxynitrile lyase from Prunus mume: Asymmetric synthesis of cyanohydrins
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
p. 10908 - 10916
(2007/10/03)

Enantioselective addition of trimethylsilyl cyanide to aldehydes catalysed by bifunctional BINOLAM-AlCl versus monofunctional BINOL-AlCl complexes
A highly enantioselective cyanation of aldehydes takes place by using a bifunctional catalyst derived from 3,3′-bis(diethylaminomethyl) substituted binaphthol (BINOLAM) and dimethylaluminium chloride. The addition is of wide scope and runs best in toluene at temperatures ranging from -20 to -40°C, in the presence of 4 A? MS and triphenylphosphine oxide as additives. The (R)- or (S)-cyanohydrins result when using (S)- or (R)-BINOLAM-AlCl complexes, respectively. The valuable ligand can be recovered by simple extractive work-up and recycled without loss of efficiency (both in terms of chemical and stereochemical yields). This methodology is applied to the Shibasaki synthesis of epothilone A. All the evidence available for the BINOLAM-AlCl enantioselective addition of TMSCN to aldehydes call for the intervention of a hydrocyanation reaction, addition of a catalytic amount of hydrogen cyanide, generated in situ, to an aldehyde, followed by O-silylation. In order to determine the role of the basic amino groups of BINOLAM, comparative studies are carried out with the monofunctional 1,1′-binaphthol-derived complex BINOL-AlCl. Graphical Abstract.
Casas, Jesús,Nájera, Carmen,Sansano, José M.,Saá, José M.
p. 10487 - 10496
(2007/10/03)

Highly enantioselective cyanosilylation of aldehydes catalyzed by novel β-amino alcohol-titanium complexes
The β-amino alcohol 1b-Ti(Oi-Pr)4 complex has been shown to catalyze the enantioselective cyanosilylation of aldehydes efficiently. In the presence of 5 mol % of 1b-Ti(Oi-Pr)4 complex catalyst, the aromatic, conjugated, heteroaromatic, and aliphatic aldehydes were converted to their corresponding trimethylsilyl ethers of cyanohydrins in 90-99% yields with up to 94% ee under mild conditions.
Li, Yan,He, Bin,Qin, Bo,Feng, Xiaoming,Zhang, Guolin
p. 7910 - 7913
(2007/10/03)

Comprehensive Step-by-Step Engineering of an (R)-Hydroxynitrile Lyase for Large-Scale Asymmetric Synthesis
A custom-made enzyme: The gene and protein sequence of a new (R)-hydroxynitrile lyase from Prunus amygdalus was cloned and engineered for recombinant production on a large scale. The enzyme is stable and active at low pH values. A rationally designed acti
Glieder, Anton,Weis, Roland,Skranc, Wolfgang,Poechlauer, Peter,Dreveny, Ingrid,Majer, Sandra,Wubbolts, Marcel,Schwab, Helmut,Gruber, Karl
p. 4815 - 4818
(2007/10/03)

BINOLAM, a recoverable chiral ligand for bifunctional enantioselective catalysis: The asymmetric synthesis of cyanohydrins
(Matrix presented) A new bifunctional catalytic system based on a monometallic aluminum complex is used for the efficient enantioselective cyanation of aldehydes. The ligand (S)- or (R)-2,2′-bis(diethylaminomethyl)-substituted binaphthol (BINOLAM) used is
Casas, Jesus,Najera, Carmen,Sansano, Jose M.,Saa, Jose M.
p. 2589 - 2592
(2007/10/03)

Tertiary pentyl groups enhance salen titanium catalyst for highly enantioselective trimethylsilylcyanation of aldehydes
tert-Pentyl groups are recognized to be highly effective steric groups that can enhance enantioselectivity of salen titanium complexes when they are used in asymmetrical cyanation of aromatic aldehydes. High ee (92-97%) has been obtained with several aldehyde substrates. Compared to its tert-butyl analogue, the tert-pentyl group has been found to improve enantioselectivity and in some cases quite dramatically.
Liang, Sidney,Bu, Xiu R.
p. 2702 - 2704
(2007/10/03)

CAL-B catalyzed enantioselective synthesis of cyanohydrins - A facile route to versatile building blocks
A straightforward process for the preparation of optically active cyanohydrins, important building blocks for the synthesis of drugs and agrochemicals, has been established. Lipase B from Candida antarctica (CAL-B) catalyzes the kinetic resolution of racemic cyanohydrin acetates under mild conditions: optimization of the process led to a user-friendly synthesis of (S)- and (R)-cyanohydrins.
Hanefeld,Li,Sheldon,Maschmeyer
p. 1775 - 1776
(2007/10/03)

Development of a family of β-amino alcohol ligands with two stereocenters for highly efficient enantioselective trimethylsilylcyanation of aldehydes
The asymmetric addition of Me3SiCN to aldehydes catalyzed by titanium(IV) complexes of N-sulfonylated derivatives of β-amino alcohols gave excellent ee's up to 96% ee.
You,Gau,Choi
p. 1963 - 1964
(2007/10/03)

Catalytic, asymmetric cyanohydrin synthesis mediated by lanthanide(III) chloride pybox complexes
Complexes formed between lanthanide trichlorides and 2,6- bis(substituted-2-oxazolin-2-yl)pyridine (pybox) ligands are effective catalysts for the enantioselective addition of trimethylsilylcyanide (TMSCN) to a range of aldehydes.
Aspinall, Helen C.,Greeves, Nicholas,Smith, Peter M.
p. 1763 - 1766
(2007/10/03)

BMPD, a novel C2-chiral 1,3-diketone ligand; synthesis and application to an asymmetric catalytic reaction
The synthesis of BMPD, 1,3-bis(2-methylferrocenyl)-propane-1,3-dione, was achieved via the Claisen condensation of a homochiral ferrocenecarboxylate and an acetylferrocene derived from the same chiral formylferrocene. Several metal complexes were prepared to exemplify the complexation ability of BMPD. A BMPD-yttrium complex was found to act as a new catalyst for silylcyanation of aldehydes with remarkable efficiency. As little as 0.2 mol% of the complex catalyzed the reaction of benzaldehyde and cyanotrimethylsilane to afford the cyanohydrin in 95% yield with 87% ee.
Abiko, Atsushi,Wang, Guo-Qiang
p. 11405 - 11420
(2007/10/03)

(S)-naproxen as a derivatizing agent to determine enantiomeric excess of cyanohydrins by HPLC
An easy, inexpensive and accurate method to determine enantiomeric excess of cyanohydrins is described. The method consists in derivatization of cyanohydrins with (S)-naproxen chloride and the products analyzed by HPLC. The results of enantiomeric excess so determined are similar to those obtained with [Eu(hfc)3], as a chiral shift reagent, and analysis by 1H- NMR of the cyanohydrins.
Solis, Aida,Luna, Hector,Perez, Herminia I.,Manjarrez, Norberto,Sanchez, Remedios,Gutierrez, Atilano
p. 8759 - 8762
(2007/10/03)

One-Pot Synthesis of Optically Active Cyanohydrin Acetates from Aldehydes via Quinidine-Catalyzed Transhydrocyanation Coupled with Lipase-Catalyzed Kinetic Resolution in Organic Solvent
A novel one-pot synthetic method was developed for the preparation of optically active cyanohydrin acetates.Racemic cyanohydrins were generated from aldehydes and acetone cyanohydrin by quinidine-catalyzed transhydrocyanation, and the resulting cyanohydrins 2a-j were then acetylated by lipase in a stereoselective manner using isopropenyl acetate as an acylating reagent.A variety of aldehydes 1a-j were successfully transformed into the corresponding cyanohydrin acetates 3a-j having 47-95percent e.e. without isolating the unstable cyanohydrins 2.Moreover, the reversible nature of base-catalyzed transhydrocyanation allows for in situ racemization of the unreacted cyanohydrins and concurrent kinetic resolution by lipase enabled the preparation of (S)-3b-d with 40-82percent e.e. in more than 50percent yield.Polymer-supported cinchona alkaloid was also used as a catalyst for this one-pot reaction and showed the comparable chemical and optical yield to that for the soluble monomeric alkaloid.The insoluble polymer and lipase were recovered by filtration and found to have almost the same catalytic activity even after four times of reuse.
Inagaki, Minoru,Hatanaka, Akihiko,Mimura, Mitsuo,Hiratake, Jun,Nishioka, Takaaki,Oda, Jun'ichi
p. 111 - 120
(2007/10/02)

A Convenient Route to (R)-α-Hydroxy Carboxylic Acids and (2R)-1-Amino-2-alkanols from (R)-Cyanohydrins
(R)-Cyanohydrins, prepared in good to excellent yields with high optical purity by enzyme-catalyzed addition of hydrogen cyanide to aldehydes in organic solvents, are hydrolyzed with concentrated hydrochloric acid at ambient temperature, usually in very high yield, without any trace of racemization to give (R)-α-hydroxy carboxylic acids.Likewise, no racemization is observed by direct reduction of the (R)-cyanohydrins with lithium aluminium hydride to give (2R)-1-amino-2-alkanols.
Ziegler, Thomas,Hoersch, Brigitte,Effenberger, Franz
p. 575 - 578
(2007/10/02)

Asymmetric Hydrocyanation of a Range of Aromatic and Aliphatic Aldehydes
A range of aryl, alkyl and heterocyclic aldehydes have been treated with hydrogen cyanide in the presence of the 'Inoue' catalyst, (R,R)- or (S,S)-cyclo.Most aryl aldehydes with electron-donating substituents in the m-or p-positions give high enantiomeric excess (e.e) values (>=80percent) but aryl aldehydes with strong electron-withdrawing substituents gave moderate e.e. values (=50percent).These moderate values are believed to be due to partial racemization of the product cyanohydrins in the presence of the mildly basic catalyst.In contrast to the reactions of aryl aldehydes, reactions of alkyl aldehydes and of ketones gave low e.e. values (=30percent) and an explanation is proposed.
Matthews, Barry R.,Jackson, W. Roy,Jayatilake, Gamini S.,Wilshire, Colin,Jacobs, Howard A.
p. 1697 - 1710
(2007/10/02)