- Novel enzymatic reduction of α-amido- and α-cyanoalkyl-β-keto esters catalyzed by ketoreductases
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An enzymatic approach for the asymmetric reduction of α-amido- and α-cyanoalkyl-β-keto esters has been developed. We have shown that NADPH-dependent ketoreductases can catalyze these transformations with excellent activity and high stereoselectivity, leading to optically pure β-hydroxy-α-amido esters as well as optically pure β-hydroxy-α-cyanoalkyl esters. With this method tert-butyl 2-acetamido-3-hydroxy-4-methylpentanoate, a valuable chiral intermediate for the synthesis of lactacystin, was obtained in high yield and excellent anti-diastereoselectivity. The ketoreductase catalyzed reduction of α-cyanomethyl- and α-cyanoethyl-β-keto esters to form the corresponding optically pure β-hydroxy esters, which are chiral intermediates for the synthesis of optically pure α-substituted γ-butyro and δ-valerolactams, was accomplished in high yield and high stereoselectivity leading to one stereoisomer out of four (>99 % de, >99 % ee, >99 % conversion).
- Giannopoulos, Vasileios,Myrtollari, Kamela,Smonou, Ioulia,Tyrikos-Ergas, Theodore
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- Potassium phosphate-ionic liquid mediated selective mono-Michael addition
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A simple and efficient process for an exclusive mono-Michael addition of active methylene compounds to conjugated esters, nitriles and ketones is developed. An ionic liquid-mediated reaction is carried out at room temperature. A reaction carried out at 60 °C resulted in a double-addition product. A mechanism is proposed and supported by P31 and DOSY NMR analysis of the used ionic liquid.
- Sawant, Anand D.,Jagadale, Suryabala D.,Desai, Uday V.,Salunkhe, Manikrao M.
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- Five Roads That Converge at the Cyclic Peroxy-Criegee Intermediates: BF3-Catalyzed Synthesis of β-Hydroperoxy-β-peroxylactones
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We have discovered synthetic access to β-hydroperoxy-β-peroxylactones via BF3-catalyzed cyclizations of a variety of acyclic precursors, β-ketoesters and their silyl enol ethers, alkyl enol ethers, enol acetates, and cyclic acetals, with H2O2. Strikingly, independent of the choice of starting material, these reactions converge at the same β-hydroperoxy-β-peroxylactone products, i.e., the peroxy analogues of the previously elusive cyclic Criegee intermediate of the Baeyer-Villiger reaction. Computed thermodynamic parameters for the formation of the β-hydroperoxy-β-peroxylactones from silyl enol ethers, enol acetates, and cyclic acetals confirm that the β-peroxylactones indeed correspond to a deep energy minimum that connects a variety of the interconverting oxygen-rich species at this combined potential energy surface. The target β-hydroperoxy-β-peroxylactones were synthesized from β-ketoesters, and their silyl enol ethers, alkyl enol ethers, enol acetates, and cyclic acetals were obtained in 30-96% yields. These reactions proceed under mild conditions and open synthetic access to a broad selection of β-hydroperoxy-β-peroxylactones that are formed selectively even in those cases when alternative oxidation pathways can be expected. These β-peroxylactones are stable and can be useful for further synthetic transformations.
- Vil, Vera A.,Gomes, Gabriel Dos Passos,Ekimova, Maria V.,Lyssenko, Konstantin A.,Syroeshkin, Mikhail A.,Nikishin, Gennady I.,Alabugin, Igor V.,Terent'Ev, Alexander O.
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p. 13427 - 13445
(2018/11/02)
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- 2,3-DISUBSTITUTED PIPERIDINE OREXIN RECEPTOR ANTAGONISTS
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The present invention is directed to 2,3-disubstituted piperidine amide compounds which are antagonists of orexin receptors, and which are useful in the treatment or prevention of neurological and psychiatric disorders and diseases in which orexin recepto
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Page/Page column 31-32
(2010/05/13)
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- Development of new DMAP-related organocatalysts for use in the Michael addition reaction of β-ketoesters in water
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A general and efficient protocol for the Michael addition reactions of β-ketoesters in pure water has been developed. The reactions are successfully catalyzed by newly designed DMAP-related organocatalysts such as 4-(didecylamino)pyridine, and the desired
- Ko, Kyungmin,Nakano, Keiji,Watanabe, Shigeru,Ichikawa, Yoshiyasu,Kotsuki, Hiyoshizo
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scheme or table
p. 4025 - 4029
(2009/11/30)
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