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.
Chiral amide derivatives of ricinoleic acid and 3-hydroxynonanoic acid synthesis and cytotoxic activity
作者:Sylwia Matysiak、Józef Kula、Alina Błaszczyk
DOI:10.1007/s00044-019-02348-y
日期:2019.7
series of chiral ricinoleic and 3-hydroxynonanoic acid derivatives were synthesized in this study using various chemical and biochemical procedures. An effective method for preparation of methyl esters of 3-hydroxynonanoic acid from castor oil or methyl ricinoleate by ozonolysis and oxidation was developed. Simple, fast, and efficientprocedures were applied to obtain different primary and secondary
N-Heterocyclic Carbene-Catalyzed Radical Reactions for Highly Enantioselective β-Hydroxylation of Enals
作者:Yuexia Zhang、Yu Du、Zhijian Huang、Jianfeng Xu、Xingxing Wu、Yuhuang Wang、Ming Wang、Song Yang、Richard D. Webster、Yonggui Robin Chi
DOI:10.1021/ja511371a
日期:2015.2.25
An N-heterocyclic carbene-catalyzed beta-hydroxylation of enals is developed. The reaction goes through a pathway involving multiple radical intermediates, as supported by experimental observations. This oxidative single-electron-transfer reaction allows for highly enantioselective access to beta-hydroxyl esters that are widely found in natural products and bioactive molecules.
Chemical Synthesis of a Glycolipid Library by a Solid-Phase Strategy Allows Elucidation of the Structural Specificity of Immunostimulation by Rhamnolipids
variations in the carbohydrate part, the lipid components, and the stereochemistry of the 3-hydroxy fattyacids was designed and synthesized. The enantioselective synthesis of the 3-hydroxy fattyacid building blocks was achieved by employing asymmetric hydrogenation of 3-oxo fattyacids. Glycolipids were prepared by this approach without any intermediary isolation steps, mostly in excellent yields. Final
obtained compounds showed antimold potential; however, the tested species of molds were more susceptible to derivatives of 3‐hydroxynonanoic acid than to amides obtained from ricinoleic acid (RA). Interestingly, hydroxamic acidsderived from RA exhibited the best activity against Candida albicans and Candida tropicalis. On the other hand, hydroxamic acidsderived from 3‐hydroxynonanoic acid showed the