- Chiral Surfactant-Type Catalyst: Enantioselective Reduction of Long-Chain Aliphatic Ketoesters in Water
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A series of amphiphilic ligands were designed and synthesized. The rhodium complexes with the ligands were applied to the asymmetric transfer hydrogenation of broad range of long-chained aliphatic ketoesters in neat water. Quantitative conversion and excellent enantioselectivity (up to 99% ee) was observed for α-, β-, γ-, δ- and ε-ketoesters as well as for α- and β-acyloxyketone using chiral surfactant-type catalyst 2. The CH/π interaction and the strong hydrophobic interaction of long aliphatic chains between the catalyst and the substrate in the metallomicelle core played a key role in the catalytic transition state. Synergistic effects between the metal-catalyzed site and the hydrophobic microenvironment of the core in the micelle contributed to high stereoselectivity. (Chemical Equation Presented).
- Lin, Zechao,Li, Jiahong,Huang, Qingfei,Huang, Qiuya,Wang, Qiwei,Tang, Lei,Gong, Deying,Yang, Jun,Zhu, Jin,Deng, Jingen
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p. 4419 - 4429
(2015/05/13)
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- Synthesis and preferred conformations of all regio- and diastereoisomeric methyl 2,3-fluorohydroxyalkanoates
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Selective syntheses of enantiopure regio- and diastereomeric methyl 2,3-fluoro-hydroxyalkanoates via four different routes employing two types of fluorination reagents are reported. The anti- and syn-3-fluoro-2- hydroxyalkanoates 1 and 3 were prepared by treating the corresponding epoxides with Olah's reagent (Py·9HF). Cyclic sulfates prepared from the enantiomeric diols were ring-opened with TBAF to give the anti- and syn-2-fluoro-3-hydroxyalkanoates 2 and 4. Thestereochemical analysis was performed mainly by NMR spectroscopy. Applying DFT/B3LYP and SCS-MP2 quantum chemical methods, the coupling constants and relative energies of conformers were calculated. Solvent effects were considered using the COSMO continuum model. Regio- and stereoselective ring opening of enantio-pure epoxides or cyclic sulfates with pyridine·9HF or TBAF delivers anti- or syn-configurated 3-fluoro-2-hydroxy- or 2-fluoro-3-hydroxyalkanoates, respectively. The relative energies of conformers were calculated by quantum chemical methods. Those of 3-fluoro-2-hydroxy isomers are influenced by intramolecular O-H·O=C hydrogen bonds, while the regioisomers show close O-H·F-C contacts. Copyright
- Husstedt, Wibke S.,Wiehle, Susanne,Stillig, Christian,Bergander, Klaus,Grimme, Stefan,Haufe, Guenter
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experimental part
p. 355 - 363
(2011/02/28)
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- New potential immunoenhancing compounds. Synthesis and pharmacological evaluation of new long-chain 2-amido-2-deoxy-D-glucose derivatives
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A series of long-chain fatty acids and the corresponding 2-hydroxy, 2-oxo, 3-hydroxy acid glucosamides were evaluated as immunomodulating compounds. In a preliminary screening, 2-[(2-ethoxycarbonyloxy)tetradecanoyl-amino]-2-deoxy-D-glucose (2b) and 2-(3-hydroxydodecanoyl-amino)-2-deoxy-D-glucose (5a) resulted to be the most effective in enhancing the glucosamine activity. The findings of in vitro-ex vivo tests (unidirectional mixed lymphocyte culture reaction and primary antibody production) and in vivo tests (delayed type hypersensitivity, protection against bacterial or fungal infection and against Sarcoma 180 or Lewis lung carcinoma transplants) were very encouraging and allowed to assume for the two substances a protective activity, presumably through the ability of activating phagocytic and NK cells.
- Valcavi,Albertoni,Brandt,Corsi,Farina,Foresta,Pascucci,Ramacci
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p. 1190 - 1195
(2007/10/02)
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