107969-82-4Relevant academic research and scientific papers
NAD(P)+-NAD(P)H Models. 59. 1,2- Versus 1,4-Reduction of β,γ-Unsaturated α-Keto Ester
Ohno, Atsuyoshi,Yasuma, Tsuneo,Nakamura, Kaoru,Oka, Shinzaburo
, p. 2905 - 2906 (1986)
Depending on the reactivity of the reducing agent, β,γ-unsaturated α-keto ester is reduced into either β,γ-unsaturated α-hydroxy ester or saturated α-keto ester as the result of 1,2- or 1,4-reduction.
Synthesis of Planar Chiral Shvo Catalysts for Asymmetric Transfer Hydrogenation
Dou, Xiaowei,Hayashi, Tamio
supporting information, p. 1054 - 1058 (2016/04/19)
A new type of planar chiral Shvo catalysts, where the chirality is based solely on different substitution flanking the C￡O function, was prepared and used for transfer hydrogenation of imines and ketones. The reduction of ketimines represented by N-(1-phe
The substrate spectrum of mandelate racemase: Minimum structural requirements for substrates and substrate model
Felfer, Ulfried,Goriup, Marian,Koegl, Marion F.,Wagner, Ulrike,Larissegger-Schnell, Barbara,Faber, Kurt,Kroutil, Wolfgang
, p. 951 - 961 (2007/10/03)
Mandelate racemase (EC 5.1.2.2) is one of the few biochemically well-characterized racemases. The remarkable stability of this cofactor-independent enzyme and its broad substrate tolerance make it an ideal candidate for the racemization of non-natural α-hydroxycarboxylic acids under physiological reaction conditions to be applied in deracemization protocols in connection with a kinetic resolution step. This review summarizes all aspects of mandelate racemase relevant for the application of this enzyme in preparative-scale biotransformations with special emphasis on its substrate tolerance. Collection and evaluation of substrate structure-activity data led to a set of general guidelines, which were used as basis for the construction of a general substrate model, which allows a quick estimation of the expected activity for a given substrate.
The first catalytic, asymmetric α-additions of isocyanides. Lewis-base-catalyzed, enantioselective Passerini-type reactions
Denmark, Scott E.,Fan, Yu
, p. 7825 - 7827 (2007/10/03)
The first, catalytic, enantioselective α-additions of isocyanides to aldehydes have been demonstrated (Passerini-type reactions). The catalytic system of silicon tetrachloride and a chiral bisphosphoramide 5a provided high yields and good to excellent enantioselectivities for the addition of tert-butyl isocyanide to a wide range of aldehydes (aromatic, olefinic, acetylenic, aliphatic). Aqueous workup afforded the α-hydroxy tert-butyl amides, whereas methanolic quench followed by basic workup afforded the ∞-hydroxy methyl esters. Copyright
Asymmetric nucleophilic acylation of aldehydes via 1,1-heterodisubstituted alkenes
Monenschein, Holger,Draeger, Gerald,Jung, Alexander,Kirschning, Andreas
, p. 2270 - 2280 (2007/10/03)
Aldehydes are asymmetrically acylated by a two step sequence that is initiated by a homologation step to 1,1-heterodisubstituted alkenes followed by asymmetric dihydroxylation. Thus, ketene O,S-acetals are efficiently prepared from aldehydes by a Peterson olefination with lithiated methoxy-phenylthiotrimethylsilyl methane 14 as the C-1 source. Although they are dihydroxylated with the Sharpless catalyst with moderate to good enantioselectivity (62-80% ee), the process is not efficient owing to the low chemical yields of the desired α-hydroxy methyl esters (7-37%). Use of the corresponding sulfoxide 24 or sulfon 25 led to an improved chemical yield of α-hydroxy methyl ester 19, but the stereoselectivity was diminished. In contrast, intermediate ketene O,O-acetals are prepared by a Horner-Wittig reaction with phosphine oxide 31 and are dihydroxylated both with good chemical and stereochemical yield. The concept is applicable to aromatic, aliphatic, and chiral aldehydes. For example, this short sequence allows exclusive and independent preparation of both diastereomeric heptoses 69 a and 69 b.
Synthesis of (R)- and (S)-2-hydroxy-3-enoic acid esters
Warmerdam,Van Den Nieuwendijk,Kruse,Brussee,Van Der Gen
, p. 20 - 24 (2007/10/03)
The synthesis of (R)- and (S)-2-hydroxy-3-enoic acid esters [(R)-1a-d and (S)-1a-c] is described. The (R) enantiomers were prepared by a Pinner synthesis from the corresponding (R)-cyanohydrins [(R)-2a-d], which in turn were obtained by R-oxynitrilase- (E.C. 4.1.2.10)-catalyzed addition of HCN to the α,β-unsaturated aldehydes 3a-d. For the preparation of the (5) enantiomers an inversion of the configuration had to be implemented. A critical evaluation of the two possible sequences: inversion of the configuration of the cyanohydrins followed by solvolysis of the nitrile function, and solvolysis of the cyanohydrins followed by inversion of the configuration of the resulting α-hydroxy esters, came out in favor of the latter pathway.
Hydroxylation of an halogen addition to the carbon carbon double bond of (R)-2-hydroxy-3-enoic acids
Yu,Simon
, p. 9035 - 9052 (2007/10/02)
Various (R)-2-hydroxy-3-enoic acids and their derivatives have been subjected to epoxidations with peracids, dihydroxylations with osmium tetroxide or methylrhenium trioxide. Depending on the derivatives and reagents applied, the diastereomeric excesses (de) achieved were in the range of 8-80%. Based on the different addition mechanisms of osmium tetroxide and methylrhenium trioxide, all four possible 2,3-dihydroxy-γ-butyrolactones, i.e. (2R,3R,4R)-, (2R,3R,4S)-, (2R,3S,4R)- and (2R,3S,4S)-γ-butyrolactones with different substituents in the 4-position could be obtained. The de values of the hydrogenation products of (R)-2-hydroxy-3-methyl-4-phenyl-3E-butenoic acid or its derivatives with a nonchiral Wilkinson catalyst depended noticeably on the derivatives used. High and extremely high stereoselectivities were observed with the halolactonization of (R)-2-hydroxy-3-enoic acids with N-bromosuccinimide or iodine leading to (2S,3R,4S)-2-hydroxy-3-halogeno-γ-butyrolactones. Br2-addition formed (2S)-2-hydroxy-3,4-dibromo carboxylic acids with stereoselectivity markedly depending on the derivatives of (R)-2-hydroxy-4-phenyl-butenoic acid applied and on the substituents at the double bond.
