Tetrahedron, asymmetry最新文献_第5页

Thermal racemization of biaryl atropisomers 二芳基反二聚体的热外消旋

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.09.006

Darshan C. Patel , Ross M. Woods , Zachary S. Breitbach , Alain Berthod , Daniel W. Armstrong

{"title":"Thermal racemization of biaryl atropisomers","authors":"Darshan C. Patel , Ross M. Woods , Zachary S. Breitbach , Alain Berthod , Daniel W. Armstrong","doi":"10.1016/j.tetasy.2017.09.006","DOIUrl":"10.1016/j.tetasy.2017.09.006","url":null,"abstract":"<div>Many biaryl compounds possess atropisomerism due to the steric hindrance of substituents at the ortho-position of the two aromatic moieties. Upon heating, atropisomers may have enough energy to surpass the rotational energy barrier and racemize. The thermal stability of five atropisomers was studied using chiral chromatography by following the change in enantiomeric excess ratio at different temperatures. The first order racemization reaction rate was obtained at a given temperature as the slope of the change in enantiomeric excess ratio versus time. For each atropisomer, the racemization rates at different temperatures led to the value of the rotational energy barrier for racemization, ΔG‡, and to the racemization half lifetime, t1/2, indicating the atropisomer thermal stability. Binaphthol started to racemize significantly at temperature of 190°C and above while binaphthyldiamine was much more stable showing little or very minor racemization up to 210°C. A chloro-substituted phenylamino-naphthol was very sensitive to thermal racemization starting at a low 40°C.</div>","PeriodicalId":22237,"journal":{"name":"Tetrahedron, asymmetry","volume":"28 11","pages":"Pages 1557-1561"},"PeriodicalIF":0.0,"publicationDate":"2017-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.09.006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75034630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 22

Diastereoselective and enantioselective alkaline-hydrolysis of 2-aryl-1-cyclohexyl acetate: a CAL-B catalyzed deacylation/acylation tandem process 2-芳基-1-乙酸环己酯的非对映选择性和非对映选择性碱水解:CAL-B催化的去酰化/酰化串联过程

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.09.010

Fatma Zahra Belkacemi , Mounia Merabet-Khelassi , Louisa Aribi-Zouioueche , Olivier Riant

{"title":"Diastereoselective and enantioselective alkaline-hydrolysis of 2-aryl-1-cyclohexyl acetate: a CAL-B catalyzed deacylation/acylation tandem process","authors":"Fatma Zahra Belkacemi , Mounia Merabet-Khelassi , Louisa Aribi-Zouioueche , Olivier Riant","doi":"10.1016/j.tetasy.2017.09.010","DOIUrl":"10.1016/j.tetasy.2017.09.010","url":null,"abstract":"<div>Candida antarctica lipase proved to be a particularly efficient lipase for the resolution of racemic 2-arylcyclohexyl acetate in hydrolysis reaction with Na2CO3 in an organic medium. The (1R,2S)-trans-2-arylcyclohexanols 2a–2d were obtained with high ee values (up to >99%) and the selectivity reached E  200. The influence of the enol ester and the solvent on (±)-trans-2-arylcyclohexanol in the CAL-B catalyzed acylation was also studied and compared with the deacylation. The CAL-B exhibits a better affinity for the alkaline hydrolysis reaction compared with acylation with the enol esters in the same organic solvents. The best conditions were applied to resolve a stereoisomeric mixture cis/trans-2-phenyl-1-cyclohexanol and its corresponding acetate by acylation and deacylation. The obtained results show a highly enantio- and diastereoselectivity of the CAL-B during the acylation and the deacylation in favor of the trans-(R)-enantiomer product. The resolution of a mixture of cis/trans-2-arylcyclohexanols was an easy, convenient approach to provide only one stereoisomer of a mixture of four with high enantiomeric excess.</div>","PeriodicalId":22237,"journal":{"name":"Tetrahedron, asymmetry","volume":"28 11","pages":"Pages 1644-1650"},"PeriodicalIF":0.0,"publicationDate":"2017-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.09.010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81147410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

A highly enantioselective [4+2] cycloaddition involving aldehydes and β,γ-unsaturated-α-keto esters 一种高度对映选择性的[4+2]环加成物，涉及醛和β，γ-不饱和-α-酮酯

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.09.019

Nanda Kumar Katakam, Yejin Kim, Allan D. Headley

引用次数: 5

anti-Selective aldol reactions of chiral alcohol substituted γ-benzyloxyl vinylogous urethanes and the synthesis of 3-benzyloxyl-4-hydroxylalkan-2-ones 手性醇取代γ-苄氧基乙烯基脲的反选择性醛醇反应及3-苄氧基-4-羟基烷烃-2-酮的合成

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.10.003

Yu-Jang Li , Chuan-Chung Chung , Pin-Zu Chen

引用次数: 0

Cystoseira algae (Fucaceae): update on their chemical entities and biological activities 水藻(岩藻科)的化学成分和生物活性研究进展

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.10.014

Carolina Bruno de Sousa , Katkam N. Gangadhar , Jorge Macridachis , Madalena Pavão , Thiago R. Morais , Lenea Campino , João Varela , João Henrique G. Lago

{"title":"Cystoseira algae (Fucaceae): update on their chemical entities and biological activities","authors":"Carolina Bruno de Sousa , Katkam N. Gangadhar , Jorge Macridachis , Madalena Pavão , Thiago R. Morais , Lenea Campino , João Varela , João Henrique G. Lago","doi":"10.1016/j.tetasy.2017.10.014","DOIUrl":"10.1016/j.tetasy.2017.10.014","url":null,"abstract":"<div>Cystoseira (Sargassaceae) is a genus of marine brown algae composed of about 40 species, which is distributed along the Eastern Atlantic and Mediterranean coasts. The biological potential of the Cystoseira genus has been investigated and several activities have been reported. Chemically, this genus contains a wide variety of secondary metabolites, such as terpenoids, steroids, phlorotannins and phenolic compounds. Additionally, other chemical components as, for instance, carbohydrates, triacylglycerols/fatty acids, pigments as well as vitamins have been identified in the studied species. Some of the isolated compounds were associated with the reported pharmacological properties, as for example antioxidant, anti-inflammatory, cytotoxicity, anticancer, cholinesterase inhibition, anti-diabetic, activities but also antibacterial, antifungal and anti-parasitic activities. In this review, we provide a comprehensive overview of the compounds isolated and identified after 1995 from the different species of Cystoseira, compiling more than 200 compounds isolated, together with their therapeutic potential.</div>","PeriodicalId":22237,"journal":{"name":"Tetrahedron, asymmetry","volume":"28 11","pages":"Pages 1486-1505"},"PeriodicalIF":0.0,"publicationDate":"2017-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.10.014","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85818764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 37

Catalytic asymmetric synthesis of Leukotriene B4 催化不对称合成白三烯B4

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.09.013

Pengfei Yang, Jiangchun Zhong, Kaijie Ji, Jingwei Yin, Shuoning Li, Siyuan Wei, Yun Zhou, Lifeng Wang, Min Wang, Qinghua Bian

引用次数: 0

Tetrahedron: Asymmetry Reports 四面体:不对称报告

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/S0957-4166(17)30518-9

引用次数: 0

Pd(II) complexes of monodentate deoxycholic acid derived binaphthyl diamido phosphites as chiral catalysts in the asymmetric Suzuki-Miyaura cross-coupling Pd(II)配合物在不对称Suzuki-Miyaura交叉偶联中的手性催化作用

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.09.012

Grazia Iannucci , Vincenzo Passarelli , Alessandro Passera , Anna Iuliano

引用次数: 5

A fast, new method to enhance the enantiomeric purity of non-racemic mixtures: self-disproportionation of enantiomers in the gas antisolvent fractionation of chlorine-substituted mandelic acid derivatives 一种快速提高非外消旋混合物对映体纯度的新方法:氯取代扁桃酸衍生物气体反溶剂分馏中对映体的自歧化

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.09.005

Márton Kőrösi , János Madarász , Tamás Sohajda , Edit Székely

{"title":"A fast, new method to enhance the enantiomeric purity of non-racemic mixtures: self-disproportionation of enantiomers in the gas antisolvent fractionation of chlorine-substituted mandelic acid derivatives","authors":"Márton Kőrösi , János Madarász , Tamás Sohajda , Edit Székely","doi":"10.1016/j.tetasy.2017.09.005","DOIUrl":"10.1016/j.tetasy.2017.09.005","url":null,"abstract":"<div>Gas antisolvent precipitation is a particle formation technique, when typically pressurized carbon dioxide is added to an organic solution resulting in immediate and high oversaturation and precipitation of fine particles. Provided that a reasonable share of the originally dissolved material remains dissolved in the carbon dioxide – organic mixed solvent, these components can be extracted during the washing phase. This method is called gas antisolvent fractionation. Gas antisolvent fractionation has been applied for the first time to enantiomeric enrichment of non-racemic mixtures, and demonstrated on the example of chlorinated mandelic acid derivatives. Due to self-disproportionation of enantiomers, the precipitated solid and the extracted fractions have different enantiomeric excesses if gas antisolvent fractionation is carried out on a non-racemic mixture. However, there is a limit in the enantiomeric excess (ee) that can be achieved correlating strongly with the atmospheric melting eutectic behavior of the compounds. Thus, if initial enantiomeric mixtures have a higher than eutectic ee, a >99% ee can be reached in the crystalline product. The strong correlation between the high-pressure experiments and the atmospheric melting eutectic behavior suggest that despite the very large oversaturation during the antisolvent precipitation, the composition of the products (i.e., the crystalline and the extracted phases) is thermodynamically determined. Technological advantages such as short operational time, or the possibility of controlling the crystal morphology suggest that the development of an efficient technique of enantiomeric purification is possible based on gas antisolvent fractionation.</div>","PeriodicalId":22237,"journal":{"name":"Tetrahedron, asymmetry","volume":"28 11","pages":"Pages 1568-1572"},"PeriodicalIF":0.0,"publicationDate":"2017-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.09.005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90279184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

Efficient 1H NMR chiral discrimination of sulfoxides caused by the dynamic nature of (R,R)-3′,3″-biBINOL (R,R)-3′，3″-biBINOL动态性质引起的亚砜的高效1H NMR手性鉴别

Tetrahedron, asymmetry Pub Date : 2017-11-15 DOI: 10.1016/j.tetasy.2017.10.008

Toshio Kawanami , Kentaro Ishizuka , Hiroshi Furuno , Yoshihito Shiota , Kazunari Yoshizawa , Junji Inanaga

引用次数: 0