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 neatwater. 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
Synthesis and Characterization of Four Diastereomers of Monorhamnolipids
作者:Ricardo Palos Pacheco、Ryan J. Eismin、Clifford S. Coss、Hui Wang、Raina M. Maier、Robin Polt、Jeanne E. Pemberton
DOI:10.1021/jacs.7b00427
日期:2017.4.12
to pure materials at the gram scale has hindered extensive characterization of rhamnolipid structure-performance behavior. Here, we present an efficient and versatile synthetic methodology from which four diastereomers of the most common monorhamnolipid, α-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate, are prepared and subsequently characterized. Exploration of their behavior at the air-water
Over 98% Optical Yield Achieved by a Heterogeneous Catalysis. Substrate Design and Analysis of Enantio-Differentiating Factors of Tartaric Acid-Modified Raney Nickel Hydrogenation
作者:Takashi Sugimura、Satoshi Nakagawa、Akira Tai
DOI:10.1246/bcsj.75.355
日期:2002.2
Tartaric acid-modified Raney nickel (TA-MRNi) is a chiral heterogeneous catalyst for the hydrogenation of prochiral ketones. An optical yield (OY) of 86% with methyl acetoacetate (1) as a substrate was improved to 94–96% by employing β-keto esters having a proper bulkiness at the γ -position. The γ -bulkiness effect contributes to a high intrinsic enantio-differentiating ability (factor-i) of the TA-MRNi catalysis. Through the study, we found the best substrate, γ -cyclopropyl-β-keto ester, the hydrogenation of which resulted in 98.6% OY. This further improvement in the OY was ascribed to a smaller contribution of non-enantio-differentiating hydrogenation (N-site catalysis) due to the substrate-specific activation of the enantio-differentiating hydrogenation by the chiral modifier. The OY of the hydrogenation of 1 was analyzed by comparing with well-behaved β-keto esters, and the contribution of the factor-i and the N-site to the OY value was evaluated to deduce the origin of the enantiodifferentiation.
Rapid Total Synthesis of Cyclic Lipodepsipeptides as a Premise to Investigate their Self‐Assembly and Biological Activity
作者:Matthias De Vleeschouwer、Davy Sinnaeve、Jos Van den Begin、Tom Coenye、José C. Martins、Annemieke Madder
DOI:10.1002/chem.201402066
日期:2014.6.16
bacteria and features self‐assembling properties. A conserved serine residue within the lactone macrocycle is exploited for initial immobilization on 2‐chlorotrityl chloride resin through ether formation with the side‐chain alcohol. Subsequent elongation proceeds through Fmoc solid‐phase peptide synthesis, including automated incorporation of the enantioselectively synthesized (R)‐3‐hydroxydecanoic acid
The Preparation of Optically Pure 3-Hydroxyalkanoic Acid. The Enantioface-differentiating Hydrogenation of the C=O Double Bond with Modified Raney Nickel. XXXVII.
作者:Masaaki Nakahata、Motomasa Imaida、Hiroshi Ozaki、Tadao Harada、Akira Tai
DOI:10.1246/bcsj.55.2186
日期:1982.7
acid–NaBr–modified Raneynickel catalyst ((R,R)-TA–NaBr–MRNi) gave methyl (R)-3-hydroxyalkanoate (CH3(CH2)nCH(OH)CH2COOCH3, n=0, 6, 8, 10, 12) in an average optical yield of 85%. After the methyl ester had been converted to dicyclohexylammonium salt of 3-hydroxyalkanoic acid, the salt was recrystallized three times from acetonitrile and then treated with acid to give optically pure (R)-3-hydroxyalkanoic acid (CH