- Chirality switching in the enantioseparation of 2-hydroxy-4-phenylbutyric acid: Role of solvents in selective crystallization of the diastereomeric salt
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Chirality switching was induced by solvents in the enantioseparation of 2-hydroxy-4-phenylbutyric acid (HPBA) via diastereomeric salt formation with an enantiopure aminoalcohol. The (S)-salt was crystallized from butanol solutions and the (R)-salt was obt
- Hirose, Takuji,Kodama, Koichi,Shitara, Hiroaki,Yi, Meng
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- Kinetic resolution of mandelate esters via stereoselective acylation catalyzed by lipase PS-30
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By using lipase PS-30 as catalyst, the kinetic resolution of a series of racemic mandelate esters has been achieved via stereoselective acylation. The value of kinetic enantiomeric ratio (E) reached up to 197.5. Substituent effect is briefly discussed.
- Chen, Peiran,Yang, Wenhong
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supporting information
p. 2290 - 2294
(2014/04/17)
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- Design and synthesis of novel 2-pyridone peptidomimetic falcipain 2/3 inhibitors
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The structure-based design, chemical synthesis and in vitro activity evaluation of various falcipain inhibitors derived from 2-pyridone are reported. These compounds contain a peptidomimetic binding determinant and a Michael acceptor terminal moiety capable of deactivating the cysteine protease active site.
- Verissimo, Edite,Berry, Neil,Gibbons, Peter,Cristiano, M. Lurdes S.,Rosenthal, Philip J.,Gut, Jiri,Ward, Stephen A.,O'Neill, Paul M.
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scheme or table
p. 4210 - 4214
(2009/04/10)
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- Catalytic, enantioselective α-additions of isocyanides: Lewis base catalyzed Passerini-type reactions
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The generality of catalytic, enantioselective α-additions of isocyanides to aldehydes has been demonstrated (Passerini-type reactions). The catalytic system of silicon tetrachloride and a chiral bisphosphoramide (R,R)-1b provided high yields and good to excellent enantioselectivities for the addition of tert-butyl isocyanide to a wide range of aldehydes (aromatic, heteroaromatic, olefinic, acetylenic, aliphatic). Aqueous workup afforded the α-hydroxy tert-butyl amides whereas a low-temperature methanol quench followed by basic workup afforded the α-hydroxy methyl esters. The reaction is also successful for other isocyanides, albeit with reduced enantioselectivity. Reaction conditions, particularly the rate of addition of the isocyanide was found to be crucial for good yields and high selectivities.
- Denmark, Scott E.,Fan, Yu
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p. 9667 - 9676
(2007/10/03)
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- The first catalytic, asymmetric α-additions of isocyanides. Lewis-base-catalyzed, enantioselective Passerini-type reactions
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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
- Denmark, Scott E.,Fan, Yu
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p. 7825 - 7827
(2007/10/03)
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- Asymmetric nucleophilic acylation of aldehydes via 1,1-heterodisubstituted alkenes
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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.
- Monenschein, Holger,Draeger, Gerald,Jung, Alexander,Kirschning, Andreas
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p. 2270 - 2280
(2007/10/03)
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- Preparation of Optically Active α-Hydroxy Acid Derivatives by Microbial Hydrolysis of Cyanohydrins and Its Application to the Synthesis of (R)-4-Dodecanolide
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Both enantiomers of aliphatic and aromatic cyanohydrins were hydrolyzed with the aid of Rhodococcus butanica ATCC 21197 to afford optically active α-hydroxy acids.The usefulness of this reaction is demonstrated by the synthesis of optically pure (R)-4-dodecanolide, a defensive secretion of rove beetles, starting from (R)-2-hydroxydecanenitrile.
- Kakeya, Hideaki,Sakai, Naoko,Sugai, Takeshi,Ohta, Hiromichi
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p. 1877 - 1881
(2007/10/02)
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- A novel synthesis of both enantiomers of α-hydroxycarboxylic esters and amides from (-)-1-chlorobutyl p-tolyl sulfoxide
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Addition of the carbanion of (-)-1-chlorbutyl p-tolyl sulfoxide to aldehydes gave two adducts, which were converted to both enantiomers of α-hydroxycarboxylic esters or amides in two steps in high overall yields.
- Satoh,Onda,Yamakawa
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p. 3567 - 3570
(2007/10/02)
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- NAD(P)+-NAD(P)H Models. 59. 1,2- Versus 1,4-Reduction of β,γ-Unsaturated α-Keto Ester
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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.
- Ohno, Atsuyoshi,Yasuma, Tsuneo,Nakamura, Kaoru,Oka, Shinzaburo
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p. 2905 - 2906
(2007/10/02)
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