- Characterization of Photodegradation Products of Bepotastine Besilate and In Silico Evaluation of Their Physicochemical, Absorption, Distribution, Metabolism, Excretion and Toxicity Properties
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Bepotastine (BPT) is a H1-receptor antagonist. It is used as a besilate salt in ophthalmic solution for allergic conjunctivitis and orally for the treatment of allergic rhinitis and urticaria/pruritus. Its systematic forced degradation study is unreported. The same was carried out in different conditions prescribed by International Conference on Harmonisation. The stressed solutions were subjected to reversed phase liquid chromatographic analysis, and BPT was observed to be labile under photobasic condition only, yielding 5 photodegradation products. The structures of the latter were elucidated from data generated by liquid chromatography–high-resolution mass spectrometry and multistage mass spectrometry. Of the 5, 4 products were further isolated and subjected to nuclear magnetic resonance spectroscopy to justify the proposed structures. Two of them, with similar accurate mass, were additionally and unambiguously characterized from their heteronuclear multiple bond correlation data, hydrogen deuterium exchange mass data, and quantum chemical analysis using density functional theory calculations. One degradation product had a structure that could only be explained by unusual rearrangement involving conversions of N-oxide into hydroxylamine, similar to Meisenheimer rearrangement. The physicochemical, as well as absorption, distribution, metabolism, excretion, and toxicity properties of BPT and its characterized photodegradation products were evaluated in silico by ADMET Predictor software.
- Singh, Dilip Kumar,Sahu, Archana,Wani, Aabid Abdullah,Bharatam, Prasad V.,Chakraborti, Asit K.,Giri, Sanjeev,Singh, Saranjit
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Read Online
- Amino alcohols using the optically active amino alcohol derivative bi- Nord complex boron - -
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Disclosed are an amino alcohol-boron-binol complex as an intermediate, including Complex 3-1-1 shown below, and a method for preparing an optically active amino alcohol by using the same, wherein a racemic amino alcohol is resolved in an enationselective manner using a boron compound and a (R)- or (S)-binol, whereby an amino alcohol derivative with high optical purity can be prepared at high yield.
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Paragraph 0064; 0071-0076; 0287-0288; 0291-0032
(2021/04/16)
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- Electronic Effect-Guided Rational Design of Candida antarctica Lipase B for Kinetic Resolution Towards Diarylmethanols
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Herein, we developed an electronic effect-guided rational design strategy to enhance the enantioselectivity of Candida antarctica lipase B (CALB) mutants towards bulky pyridyl(phenyl)methanols. Compared to W104A mutant previously reported with reversed S-stereoselectivity toward sec-alcohols, three mutants (W104C, W104S and W104T) displayed significant improvement of S-enantioselectivity in the kinetic resolution (KR) of various phenyl pyridyl methyl acetates due to the increased electronic effects between pyridyl and polar residues. The electronic effects were also observed when mutating other residues surrounding the stereospecificity pocket of CALB, such as T42A, S47A, A281S or A281C, and can be used to manipulate the stereoselectivity. A series of bulky pyridyl(phenyl) methanols, including S-(4-chlorophenyl)(pyridin-2-yl) methanol (S-CPMA), the intermediate of bepotastine, were obtained in good yields and ee values. (Figure presented.).
- Li, Dan-Yang,Lou, Yu-Jiao,Xu, Jian,Chen, Xiao-Yang,Lin, Xian-Fu,Wu, Qi
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p. 1867 - 1872
(2021/02/12)
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- Molecular switch manipulating Prelog priority of an alcohol dehydrogenase toward bulky-bulky ketones
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Structure-guided rational design revealed the molecular switch manipulating the Prelog and anti-Prelog priorities of an NADPH-dependent alcohol dehydrogenase toward prochiral ketones with bulky and similar substituents. Synergistic effects of unconserved residues at 214 and 237 in small and large substrate binding pockets were proven to be vital in governing the stereoselectivity. The ee values of E214Y/S237A and E214C/S237 G toward (4-chlorophenyl)-(pyridin-2-yl)-methanone were 99.3% (R) and 78.8% (S) respectively. Substrate specificity analysis revealed that similar patterns were also found with (4’-chlorophenyl)-phenylmethanone, (4’-bromophenyl)-phenylmethanone and (4’-nitrophenyl)-phenylmethanone. This study provides valuable evidence for understanding the molecular mechanism on enantioselective recognition of prochiral ketones by alcohol dehydrogenase.
- Xu, Guochao,Dai, Wei,Wang, Yue,Zhang, Lu,Sun, Zewen,Zhou, Jieyu,Ni, Ye
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- Engineering an alcohol dehydrogenase with enhanced activity and stereoselectivity toward diaryl ketones: Reduction of steric hindrance and change of the stereocontrol element
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Steric hindrance in the binding pocket of an alcohol dehydrogenase (ADH) has a great impact on its activity and stereoselectivity simultaneously. Due to the subtle structural difference between two bulky phenyl substituents, the asymmetric synthesis of diaryl alcohols by bioreduction of diaryl ketones is often hindered by the low activity and stereoselectivity of ADHs. To engineer an ADH with practical properties and to investigate the molecular mechanism behind the asymmetric biocatalysis of diaryl ketones, we engineered an ADH from Lactobacillus kefiri (LkADH) to asymmetrically catalyse the reduction of 4-chlorodiphenylketones (CPPK), which are not catalysed by the wild type (WT) enzyme. Mutants seq1-seq5 with gradually increased activity and stereoselectivity were obtained through iterative "shrinking mutagenesis." The final mutant seq5 (Y190P/I144V/L199V/E145C/M206F) demonstrated the highest activity and excellent stereoselectivity of >99% ee. Molecular simulation analyses revealed that mutations may enhance the activity by eliminating steric hindrance, inducing a more open binding loop and constructing more noncovalent interactions. The pro-R pose of CPPK with a halogen bond formed a pre-reaction conformation more easily than the pro-S pose, resulting in the high ee of (R)-CPPO in seq5. Moreover, different halogen bonds formed due to the different positions of chlorine substituents, resulting in opposite substrate binding orientation and stereoselectivity. Therefore, the stereoselectivity of seq5 was inverted toward ortho- rather than para-chlorine substituted ketones. These results indicate that the stereocontrol element of LkADH was changed to recognise diaryl ketones after steric hindrance was eliminated. This study provides novel insights into the role of steric hindrance and noncovalent bonds in the determination of the activity and stereoselectivity of enzymes, and presents an approach producing key intermediates of chiral drugs with practical potential.
- Chen, Rong,Huang, Jiankun,Meng, Xiangguo,Shao, Lei,Wu, Kai,Yang, Zhijun
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p. 1650 - 1660
(2020/04/09)
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- Conformational Dynamics-Guided Loop Engineering of an Alcohol Dehydrogenase: Capture, Turnover and Enantioselective Transformation of Difficult-to-Reduce Ketones
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Directed evolution of enzymes for the asymmetric reduction of prochiral ketones to produce enantio-pure secondary alcohols is particularly attractive in organic synthesis. Loops located at the active pocket of enzymes often participate in conformational changes required to fine-tune residues for substrate binding and catalysis. It is therefore of great interest to control the substrate specificity and stereochemistry of enzymatic reactions by manipulating the conformational dynamics. Herein, a secondary alcohol dehydrogenase was chosen to enantioselectively catalyze the transformation of difficult-to-reduce bulky ketones, which are not accepted by the wildtype enzyme. Guided by previous work and particularly by structural analysis and molecular dynamics (MD) simulations, two key residues alanine 85 (A85) and isoleucine 86 (I86) situated at the binding pocket were thought to increase the fluctuation of a loop region, thereby yielding a larger volume of the binding pocket to accommodate bulky substrates. Subsequently, site-directed saturation mutagenesis was performed at the two sites. The best mutant, where residue alanine 85 was mutated to glycine and isoleucine 86 to leucine (A85G/I86L), can efficiently reduce bulky ketones to the corresponding pharmaceutically interesting alcohols with high enantioselectivities (～99% ee). Taken together, this study demonstrates that introducing appropriate mutations at key residues can induce a higher flexibility of the active site loop, resulting in the improvement of substrate specificity and enantioselectivity. (Figure presented.).
- Liu, Beibei,Qu, Ge,Li, Jun-Kuan,Fan, Wenchao,Ma, Jun-An,Xu, Yan,Nie, Yao,Sun, Zhoutong
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supporting information
p. 3182 - 3190
(2019/05/15)
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- Two enantiocomplementary ephedrine dehydrogenases from arthrobacter sp. TS-15 with broad substrate specificity
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The recently identified pseudoephedrine and ephedrine dehydrogenases (PseDH and EDH, respectively) from Arthrobacter sp. TS-15 are NADH-dependent members of the oxidoreductase superfamily of short-chain dehydrogenases/reductases (SDRs). They are specific for the enantioselective oxidation of (+)-(S) N-(pseudo)ephedrine and (-)-(R) N-(pseudo)ephedrine, respectively. Anti-Prelog stereospecific PseDH and Prelog-specific EDH catalyze the regio- A nd enantiospecific reduction of 1-phenyl-1,2-propanedione to (S)-phenylacetylcarbinol and (R)-phenylacetylcarbinol with full conversion and enantiomeric excess of >99%. Moreover, they perform the reduction of a wide range of aryl-aliphatic carbonyl compounds, including ketoamines, ketoesters, and haloketones, to the corresponding enantiopure alcohols. The highest stability of PseDH and EDH was determined to be at a pH range of 6.0-8.0 and 7.5-8.5, respectively. PseDH was more stable than EDH at 25 °C with half-lives of 279 and 38 h, respectively. However, EDH is more stable at 40 °C with a 2-fold greater half-life than at 25 °C. The crystal structure of the PseDH-NAD+ complex, refined to a resolution of 1.83 ?, revealed a tetrameric structure, which was confirmed by solution studies. A model of the active site in complex with NAD+ and 1-phenyl-1,2-propanedione suggested key roles for S143 and W152 in recognition of the substrate and positioning for the reduction reaction. The wide substrate spectrum of these dehydrogenases, combined with their regio- A nd enantioselectivity, suggests a high potential for the industrial production of valuable chiral compounds.
- Shanati, Tarek,Lockie, Cameron,Beloti, Lilian,Grogan, Gideon,Ansorge-Schumacher, Marion B.
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p. 6202 - 6211
(2019/08/15)
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- A (S)- phenyl (pyridine -2 - yl) methanol derivative preparation method (by machine translation)
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The invention discloses a (S)- (pyridine - 2 - yl) phenyl methanol derivatives of the preparation method, the process is: in the argon atmosphere and 10 - 40 °C temperature, metal M complex with a chiral ligand L* In A added to the solvent, stirring the reaction 0.5 - 6 hours, to obtain the catalyst [M]/ L* ; The metal M in the complex metal M is Ru, Rh, Pd Ir or in any of the a; to the autoclave is sequentially added in the phenyl (pyridin - 2 - yl) methanone derivatives, the obtained catalyst [M]/ L* , Solvent B and alkali, for 0 - 100 °C temperature and 0.1 - 10.0 mpa of reaction under a hydrogen pressure of 2 - 24 hours, after the reaction, the reaction solution concentrated under reduced pressure to recover solvent B, add water, extracted with ethyl acetate, the organic phase and aqueous phase liquid, drying of the organic phase, desolvation prepared (S)- (pyridine - 2 - yl) phenyl methanol derivatives. The catalyst of the present invention asymmetric hydrogenation reaction, a reaction product of high yield, high enantio-selectively generating (S)- (pyridine - 2 - yl) phenyl methanol derivatives, in the ee value of 99% or more. (by machine translation)
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Paragraph 0094-0100
(2019/07/04)
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- Highly Enantioselective Hydrogenation of Non- ortho-Substituted 2-Pyridyl Aryl Ketones via Iridium- f-Diaphos Catalysis
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This work disclosed a highly enantioselective hydrogenation of non-ortho-substituted 2-pyridyl aryl ketones via Ir/f-diaphos catalysis. This catalytic system allows for full control over the configuration of the stereocenter, affording two enantiomers of the desired products with extremely high enantioselectivity (up to >99% ee in most cases) and excellent reactivity (TON of up to 19600, TOF of 1633 h-1) under mild conditions. Density functional theory calculations and control experiments revealed that the relay hydrogen bonding among the solvent isopropanol, substrate, and ligand is crucial for high ee's.
- Nian, Sanfei,Ling, Fei,Chen, Jiachen,Wang, Ze,Shen, Haiwei,Yi, Xiao,Yang, Yun-Fang,She, Yuanbin,Zhong, Weihui
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supporting information
p. 5392 - 5396
(2019/08/01)
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- Preparation technology of bepotastine medical intermediate
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The invention discloses a preparation technology of a bepotastine medical intermediate. The technology comprises the following processes: under an argon atmosphere and 0 to 60 DEG C, adding a metal Mcomplex and a chiral ligand L into solvent A, and stirring and reacting for 0.5 to 6 hours to prepare a catalyst [M]/L, wherein metal M is Ru, Rh, Ir or Pd; adding (4-chlorophenyl)(pyridin-2-yl)ketone, the prepared catalyst [M]/L, solvent B and alkali into an autoclave, and reacting for 2 to 24 hours under the temperature of 0 to 100 DEG C and the hydrogen pressure of 0.1 to 10.0 MPa; after a reaction is completed, performing vacuum concentration on reaction liquid to recover the solvent B; and then adding a proper amount of water, performing extraction by ethyl acetate, performing liquid separation to obtain an organic phase and a water phase, performing drying and desolvation on the organic phase to prepare (S)-(4-chlorophenyl)(pyridin-2-yl)methanol, namely the bepotastine medical intermediate. Compared with a conventional technology for preparing the (S)-(4-chlorophenyl)(pyridin-2-yl)methanol by a chiral separation method, a method involved in the invention has the characteristics that the consumption of the catalyst is low; the yield and an ee (enantiomeric excess) value are high; and the like; in addition, reaction conditions are mild; the operation is simple and convenient; and industrial production is easy to realize.
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Page/Page column 9-14
(2019/06/30)
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- Fine tuning the enantioselectivity and substrate specificity of alcohol dehydrogenase from Kluyveromyces polysporus by single residue at 237
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Here, S237 was identified to be important in fine tuning the substrate specificity and enantioselectivity of alcohol dehydrogenase from Kluyveromyces polysporus (KpADH). In the reduction of a diaryl ketone, (4-chlorophenyl)-(pyridin-2-yl)-methanone (1a), the highest and lowest enantioselectivity of 96.1% and 27.0% e.e. (R) were obtained with S237A and S237C. Kinetic parameters analysis revealed that S237G, S237A, S237H and S237D displayed improved kcat/Km toward 1a. Various prochiral ketones, including acetophenone, 4-chloroacetophenone and ethyl 2-oxo-4-phenylbutyrate could be asymmetrically reduced by S237C, S237G and S237E with > 99% e.e. This study provides guidance for the application of KpADH in the preparation of chiral secondary alcohols.
- Wang, Yue,Dai, Wei,Liu, Yongmei,Zhang, Zhongwei,Zhou, Jieyu,Xu, Guochao,Ni, Ye
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- Hydroclassified Combinatorial Saturation Mutagenesis: Reshaping Substrate Binding Pockets of KpADH for Enantioselective Reduction of Bulky-Bulky Ketones
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A hydroclassified combinatorial saturation mutagenesis (HCSM) strategy was proposed for reshaping the substrate binding pocket by dividing 20 amino acids into four groups based on their hydrophobicity and size. These smart HCSM libraries could significantly reduce screening effort especially for the simultaneous mutagenesis of three or more residues and lacking high throughput screening methods. Employing HCSM strategy, the stereoselectivity of KpADH, an alcohol dehydrogenase from Kluyveromyces polysporus, was efficiently improved to 99.4% ee. (4-Chlorophenyl)(pyridin-2-yl)methanone (CPMK), generally regarded as a "hard-to-reduce" ketone, was used as a model substrate, and its corresponding chiral alcohol products could be utilized as antihistamine precursors. The best variant 50C10 displayed higher binding affinity and catalytic efficiency toward CPMK with KM/kcat of 59.3 s-1·mM-1, 3.51-fold that of KpADH. Based on MD simulations, increased difference between two binding pockets, enhanced hydrophobicity, and π-π and halogen-alkyl interactions were proposed to favor the enantioselective recognition and substrate binding in 50C10. Substrate spectrum analysis revealed that 50C10 exhibited improved enantioselectivity toward diaryl ketones especially with halo- or other electron-withdrawing groups. As much as 500 mM CPMK could be asymmetrically reduced into chiral diaryl alcohols with ee of 99.4% and a space-time yield of 194 g·L-1·d-1 without addition of external NADP+. This study provides an effective mutagenesis strategy for the protein engineering of substrate specificity and enantioselectivity.
- Xu, Guo-Chao,Wang, Yue,Tang, Ming-Hui,Zhou, Jie-Yu,Zhao, Jing,Han, Rui-Zhi,Ni, Ye
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p. 8336 - 8345
(2018/09/18)
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- Structural Insight into Enantioselective Inversion of an Alcohol Dehydrogenase Reveals a "polar Gate" in Stereorecognition of Diaryl Ketones
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Diaryl ketones are important building blocks for synthesizing pharmaceuticals and are generally regarded as "difficult-to-reduce" ketones due to the large steric hindrance of their two bulky aromatic side chains. Alcohol dehydrogenase from Kluyveromyces polyspora (KpADH) has been identified as a robust biocatalyst due to its high conversion of diaryl ketone substrate (4-chlorophenyl)(pyridine-2-yl)ketone (CPMK) with a moderate R-selectivity of 82% ee. To modulate the stereoselectivity of KpADH, a "polarity scanning" strategy was proposed, in which six key residues inside and at the entrance of the substrate binding pocket were identified. After iterative combinatorial mutagenesis, variants Mu-R2 and Mu-S5 with enhanced (99.2% ee, R) and inverted (97.8% ee, S) stereoselectivity were obtained. The crystal structures of KpADH and two mutants in complex with NADPH were resolved to elucidate the evolution of enantioselective inversion. Based on MD simulation, Mu-R2-CPMKProR and Mu-S5-CPMKProS were more favorable in the formation of prereaction states. Interestingly, a quadrilateral plane formed by α-carbons of four residues (N136, V161, C237, and G214) was identified at the entrance of the substrate binding pocket of Mu-S5; this plane acts as a "polar gate" for substrates. Due to the discrepancy in charge characteristics between chlorophenyl and pyridine substituents, the pro-S orientation of CPMK is defined when it passes through the "polar gate" in Mu-S5, whereas the similar plane in wild-type is blocked by several aromatic residues. Our result paves the way for engineering stereocomplementary ADH toward bulky diaryl ketones and provides structural insight into the mechanism of stereoselective inversion.
- Zhou, Jieyu,Wang, Yue,Xu, Guochao,Wu, Lian,Han, Ruizhi,Schwaneberg, Ulrich,Rao, Yijian,Zhao, Yi-Lei,Zhou, Jiahai,Ni, Ye
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supporting information
p. 12645 - 12654
(2018/10/05)
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- Iridium-Catalyzed Highly Enantioselective Transfer Hydrogenation of Aryl N-Heteroaryl Ketones with N-Oxide as a Removable ortho-Substituent
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A highly enantioselective transfer hydrogenation of non-ortho-substituted aryl N-heteroaryl ketones, using readily available chiral diamine-derived iridium complex (S,S)-1f as a catalyst and sodium formate as a hydrogen source in a mixture of H2O/i-PrOH (v/v = 1:1) under ambient conditions, is described. The chiral aryl N-heteroaryl methanols were obtained with up to 98.2% ee by introducing an N-oxide as a removable ortho-substituent. In contrast, no more than 15.1% ee was observed in the absence of an N-oxide moiety. Furthermore, the practical utility of this protocol was also demonstrated by gram-scale asymmetric synthesis of bepotastine besilate in 51% total yield and 99.9% ee.
- Liu, Qixing,Wang, Chunqin,Zhou, Haifeng,Wang, Baigui,Lv, Jinliang,Cao, Lu,Fu, Yigang
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supporting information
p. 971 - 974
(2018/02/23)
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- Chiral synthesis method of bepotastine besilate intermediate
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The invention discloses a chiral synthesis method of a bepotastine besilate intermediate. The chiral synthesis method comprises the following step: by taking (4-chlorphenyl) (pyridine-2-radical) ketone as a raw material, under the action of alkali and a catalyst, carrying out hydrogenation stirring reaction in a solvent, so as to obtain (S)-(4-chlorphenyl) (pyridine-2-radical) methanol. Accordingto the method disclosed by the invention, a high-purity product can be obtained only by one-step catalytic hydrogenation reaction of a production process, so that the process period is greatly shortened; the chiral synthesis method has the characteristics of simple synthesis line, small use amount of the catalyst, stable reaction process, environmental friendliness, economy and the like, and has an extremely industrial application value in the aspect production and preparation of the (S)-(4-chlorphenyl) (pyridine-2-radical) methanol.
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Paragraph 0043; 0044; 0045; 0046
(2018/05/16)
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- Bifunctional Oxo-Tethered Ruthenium Complex Catalyzed Asymmetric Transfer Hydrogenation of Aryl N-Heteroaryl Ketones
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A facile asymmetric transfer hydrogenation of ortho-substituted aryl N-heteroaryl ketones and non-ortho-substituted N-oxide of aryl N-heteroaryl ketones using a readily available oxo-tethered ruthenium complex as a catalyst and sodium formate as a hydrogen source in an aqueous solution has been discovered. A variety of chiral aryl N-heteroaryl methanols were obtained with up to 99.9% ee.
- Wang, Baigui,Zhou, Haifeng,Lu, Guoren,Liu, Qixing,Jiang, Xiaolan
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p. 2094 - 2097
(2017/04/28)
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- Asymmetric syntheses method of ophthalmologic drug bepotastine besilate
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The invention relates to an asymmetric synthesis method of an ophthalmologic drug pylistramine besylate. The method concretely comprises the following steps: oxidizing (4-chlorophenyl)(2-pyridyl)methanone to obtain (4-chlorophenyl)(2-pyridyl)ketone-N-oxide; carrying out asymmetric transfer hydrogenation reduction on the (4-chlorophenyl)(2-pyridyl)ketone-N-oxide through using a complex of monosulfonyl chiral diamine and metallic ruthenium, rhodium and iridium as a catalyst and a sodium formate or formic acid and triethylamine mixture or isopropanol as a hydrogen source in order to prepare (S)-(4-chlorophenyl)(2-pyridyl)methanol-N-oxide; reducing the (S)-(4-chlorophenyl)(2-pyridyl)methanol-N-oxide to prepare (S)-(4-chlorophenyl)(2-pyridyl)methanol; and condensing the (S)-(4-chlorophenyl)(2-pyridyl)methanol and ethyl 4-(4-bromopiperidine-1-yl)butyrate to obtain the ophthalmologic drug pylistramine besylate. The total yield is 61.6%.
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Paragraph 0048; 0049; 0050; 0051
(2017/09/01)
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- Asymmetric synthesis method for anti-allergy drug carbinoxamine
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The invention relates to an asymmetric synthesis method for an anti-allergy drug carbinoxamine. The method specifically comprises the following steps: oxidizing (4-chlorophenyl)(2-pyridyl)ketone to obtain (4-chlorophenyl)(2-pyridyl)ketone-N-oxide; by taking monosulfonylated chiral diamine and metal ruthenium/rhodium/iridium complex as catalysts and sodium formate or a formic acid and triethylamine mixture or isopropanol as a hydrogen source, reducing the (4-chlorophenyl)(2-pyridyl)ketone-N-oxide through asymmetry transfer hydrogenation to prepare (S)-(4-chlorophenyl)(2-pyridyl)methanol-N-oxide; reducing the (S)-(4-chlorophenyl)(2-pyridyl)methanol-N-oxide to obtain (S)-(4-chlorophenyl)(2-pyridyl)methanol; and performing etherification reaction on the (S)-(4-chlorophenyl)(2-pyridyl)methanol and 2-chloro-N,N-dimethylethylamine to obtain the product, wherein the overall yield is 74.6%.
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Paragraph 0040; 0041
(2017/07/21)
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- Rhodium Catalyzed Asymmetric Hydrogenation of 2-Pyridine Ketones
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Catalyzed by [Rh(COD)Binapine]BF4, the asymmetric hydrogenation of 2-pyridine ketones has been achieved with excellent enantioselectivities (enantiomeric excesses up to 99%) under mild conditions. This method is suitable for various kinds of 2-pyridine ketones and their derivatives. A number of enantiomerically pure chiral 2-pyridine-aryl/alkyl alcohols were prepared through hydrogenation, which can be used directly in organic synthesis.
- Yang, Hailong,Huo, Ningning,Yang, Ping,Pei, Hao,Lv, Hui,Zhang, Xumu
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p. 4144 - 4147
(2015/09/15)
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- Synthesis of chiral pyridyl alcohols using a two-step catalytic approach
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Chira l pyridyl alcohols have been prepared by developing a two-step approach that uses the asymmetric cyanation of aldehydes to give cyanohydrins and subsequent [2+2+2]-cyclotrimerization reaction with acetylene. Georg Thieme Verlag Stuttgart.
- Heller, Barbara,Redkin, Dmitry,Gutnov, Andrey,Fischer, Christine,Bonrath, Werner,Karge, Reinhard,Hapke, Marko
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- Enzyme-catalyzed enantioselective diaryl ketone reductions
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(Chemical Equation Presented) The synthesis of diarylmethanols via the reduction of a range of substituted benzophenone and benzoylpyridine derivatives with ketoreductase enzymes (KREDs) has afforded chiral products with high yield (>90%) and ee (up to >99%). Ortho, meta, and para substitutions with a variety of electron-donating, electron-withdrawing, and halogen groups were examined. Substitution at the ortho position and/or highly electronically dissymmetric molecules were not required for good selectivity, as is the case with conventional chemical catalyst reductions.
- Truppo, Matthew D.,Pollard, David,Devine, Paul
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p. 335 - 338
(2007/10/03)
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- Highly Enantioselective Hydrogenation of Aromatic-Heteroaromatic Ketones
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(Equation presented) Asymmetric hydrogenation of ketone 1 using trans-RuCl2[(R)-xylbinap][(R)-daipen] (3) as a catalyst afforded secondary alcohol 2 quantitatively and in 99.4% ee. Further exploration of the effect of the thiazole ring substitution revealed that the catalyst was highly effective for the enantioselective hydrogenation of 5-benzoyl thiazoles, which afforded corresponding alcohols in 92-99% ee. The same protocol was applicable to a variety of aromatic-heteroaromatic ketones to generate secondary alcohols in excellent enantioselectivities.
- Chen, Cheng-Yi,Reamer, Robert A.,Chilenski, Jennifer R.,McWilliams, Chris J.
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p. 5039 - 5042
(2007/10/03)
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- Asymmetric synthesis of (S)-carbinoxamine. New aspects of oxazaborolidine-catalyzed enantioselective carbonyl reduction
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A new process has been developed for the highly enantioselective catalytic reduction of 2-aroylpyridines and successfully applied to the synthesis of (S)-carbinoxamine (1), a therapeutically important histamine H1 antagonist. Related enantioselective reductions of 4-aroylpyridines and ortho-substituted benzophenones are also described.
- Corey,Helal, Christopher J.
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p. 5675 - 5678
(2007/10/03)
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- Effect of inhibitor or immobilization on reduction of benzoylpyridines by baker's yeast
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The stereochemical course of the reduction of benzolpyridine derivatives (1a-e) by baker's yeast can be modified by immobilization or by treating the reduction system with allyl alcohol or ethyl chloroacetate.
- Takemoto, Masumi,Yamamoto, Yuichi,Achiwa, Kazuo
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p. 853 - 855
(2007/10/03)
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- Preparation, Absolute Configuration and Conformation of Some α-Aryl-2-pyridylmethanols
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The syntheses of five optically active α-aryl-2-pyridylmethanols 1-5 are described.It is shown by means of chemical correlation with the known (-)-(α-R,2S)-α-phenyl-2-piperidylmethanol 6 that all levo-rotatory isomers 1-4 are of R configuration.It is also found via the relative integral intensities in the infrared spectra of the bands due to free and intramolecularly bonded hydroxyl groups in the compounds 1-4 and the free hydroxyl groups in the model compounds 7-10, that the population of the conformers with an intramolecular OH...N bond in compounds 1-4 exceds 80percent.
- Bojadziev, Stefan E.,Tsankov, Dimiter T.,Ivanov, Petko M.,Berova, Nikolina D.
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p. 2651 - 2656
(2007/10/02)
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