Tetrahedron, asymmetry最新文献_第9页

Strategies for using NMR spectroscopy to determine absolute configuration 使用核磁共振波谱确定绝对构型的策略

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.09.009

Thomas J. Wenzel

引用次数: 15

Tetrahedron: Asymmetry Reports 四面体:不对称报告

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/S0957-4166(17)30493-7

引用次数: 0

Cumulative author index 累计作者索引

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/S0957-4166(17)30494-9

引用次数: 0

Stereochemistry abstracts 立体化学文摘

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/S0957-4166(17)30492-5

引用次数: 0

Some experimental aspects of absolute configuration determination using single crystal X-ray diffraction 用单晶x射线衍射测定绝对构型的一些实验方面

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.08.016

Amber L. Thompson , Sarah F. Jenkinson , George W.J. Fleet

引用次数: 5

Some new protocols for the assignment of absolute configuration by NMR spectroscopy using chiral solvating agents and CDAs 用手性溶剂化剂和cda进行核磁共振绝对构型的新方法

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.09.017

Sandeep Kumar Mishra, Nagarajarao Suryaprakash

{"title":"Some new protocols for the assignment of absolute configuration by NMR spectroscopy using chiral solvating agents and CDAs","authors":"Sandeep Kumar Mishra, Nagarajarao Suryaprakash","doi":"10.1016/j.tetasy.2017.09.017","DOIUrl":"10.1016/j.tetasy.2017.09.017","url":null,"abstract":"<div>The utility of enantiopure BINOL (1,10-Bi-2-naphthol), in a ternary ion-pair complex, which is obtained using a carboxylic acid and an organic base, as a versatile chiral solvating agent (CSA) has been demonstrated for chiral analysis and the absolute configuration assignment of hydroxy acids. Another protocol where the utility of NOBIN as a CSA has been developed for discrimination and absolute configuration assignment of acids, hydroxy acids and their derivatives with a distinct strategy where a third ingredient, p-toluenesulfonic acid (p-TsOH) serves as a linker. In addition some three component chiral derivatization protocols have been introduced, such as the use of 2-formylphenylboronic acid and enantiopure mandelic acid or a primary amine for the determination of the configuration of primary amines and hydroxy acids, respectively. A simple, rapid and highly efficient three component chiral derivatizing protocol has also been discussed which was developed for assigning the absolute configuration of chiral α-hydroxy acids and their derivatives, which involves the coupling of 2-formylphenylboronic acid with (R)-[1,1-binaphthalene]-2,2-diamine, and (S)-[1,1-binaphthalene]-2,2-diamine separately. In a few examples, the DFT based theoretical calculations have been carried out to determine the geometry optimized structures of the complexes.</div>","PeriodicalId":22237,"journal":{"name":"Tetrahedron, asymmetry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.09.017","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88605905","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: 9

Special Issue in memory of Howard D Flack, who died suddenly in February 2017 纪念霍华德·D·弗莱克的特刊，他于2017年2月突然去世

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.10.002

David J. Watkin

引用次数: 2

Nucleophilic additions on acetyldioxanes derived from (−)-(1R)-myrtenal used as chiral auxiliaries: substituent effects on the stereochemical outcome 作为手性助剂的(−)-(1R)桃金娘醛衍生的乙酰二恶烷上的亲核加成物:取代基对立体化学结果的影响

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.07.008

Elvia Becerra-Martínez , Francisco Ayala-Mata , Pedro Velázquez-Ponce , Manuel E. Medina , Hugo A. Jiménez-Vazquez , Pedro Joseph-Nathan , L. Gerardo Zepeda

{"title":"Nucleophilic additions on acetyldioxanes derived from (−)-(1R)-myrtenal used as chiral auxiliaries: substituent effects on the stereochemical outcome","authors":"Elvia Becerra-Martínez , Francisco Ayala-Mata , Pedro Velázquez-Ponce , Manuel E. Medina , Hugo A. Jiménez-Vazquez , Pedro Joseph-Nathan , L. Gerardo Zepeda","doi":"10.1016/j.tetasy.2017.07.008","DOIUrl":"10.1016/j.tetasy.2017.07.008","url":null,"abstract":"<div>The synthesis of acetyldioxanes 4 and 9a starting from (−)-(1R)-myrtenal is described. The products were treated with a representative series of nucleophilic reagents (RMgX, RLi, NaBH4 and LiAlH4) to assess the effect of the substituent at C-3 on the stereochemical outcome. It was observed that the nucleophiles preferred the re-face of the C<img>O group when the equatorial substituent at C-3 was a methyl group, whereas a phenyl group at the same position induced the addition through the si-face, thus allowing access to either desired stereochemistry of a final product. This behavior suggests that the formation of the expected Cram-chelated coordination complex takes a coplanar orientation with the C-3 equatorial substituent. Moreover, Grignard reagents were the most stereoselective nucleophiles. The stereochemistry of the addition was established by X-ray diffraction and chemical correlation.</div>","PeriodicalId":22237,"journal":{"name":"Tetrahedron, asymmetry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.07.008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76879328","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: 3

Verification study for an empirical rule in diverse helical conformational behaviors of asymmetric 1,2-diacyl-sn-glycerols in the solution state 不对称1,2-二酰基- sn -甘油溶液中不同螺旋构象行为经验规律的验证研究

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.09.021

Yoshihiro Nishida , Yuan Mengfei , Kaito Fujisawa , Sakura Kitagawa , Hirofumi Dohi , Hirotaka Uzawa

{"title":"Verification study for an empirical rule in diverse helical conformational behaviors of asymmetric 1,2-diacyl-sn-glycerols in the solution state","authors":"Yoshihiro Nishida , Yuan Mengfei , Kaito Fujisawa , Sakura Kitagawa , Hirofumi Dohi , Hirotaka Uzawa","doi":"10.1016/j.tetasy.2017.09.021","DOIUrl":"10.1016/j.tetasy.2017.09.021","url":null,"abstract":"<div>Cell-membrane glycerophospholipids and glycolipids have a common asymmetric skeleton of 1,2-diacyl-sn-glycerols. The 1,2-diacyl moiety in solutions permits a rapid equilibrium among three helical conformers, namely gt(+), gg(−), and tg, to display diverse conformational properties. The conformational property changes variably not only by head groups at the sn-3 position, but also by the solvent conditions applied. Recently, we came across an empirical rule in the conformational diversity in the solution state when we assumed the term of ‘helical disparity’ for the equilibrium between gt(+) and gg(−) conformers with reversed helical signs for each other. The sign and magnitude of the helical disparity (%) governs the (+)- or (−)-chirality around the lipid tail and corresponds to the magnitude of the exciton couplet CD (circular dichroism) bands. The empirical rule expresses that the disparity (%) changes linearly by the function of gt(+) population (%). Herein, the rule was verified by 1H NMR spectroscopy using different types of 1,2-diacyl-sn-glycerols as model compounds. The present paper describes that the rule is formulated with a general equation (Eq-1): ‘helical disparity (%)’ = [gt(+)−gg(−)] (%) = A[gt(+)−B], in which A and B are constants taking values around 1.3 and 38, respectively. This rule is maintained regardless of the 1,2-diacyl and sn-3 substituent groups as far as examined here, while affording several exceptions. With Eq-1 (A = 1.3, B = 38), a conformational diagram can be obtained. This allows us to overview the diverse helical conformational properties of the asymmetric 1,2-diacyl-sn-glycerols in the solutions state.</div>","PeriodicalId":22237,"journal":{"name":"Tetrahedron, asymmetry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.09.021","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76294121","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: 1

Ferrocene derivatives of liquid chiral molecules allow assignment of absolute configuration by X-ray crystallography 二茂铁衍生物的液体手性分子允许分配绝对构型的x射线晶体学

Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.09.002

Philipp M. Holstein , Julian J. Holstein , Eduardo C. Escudero-Adán , Olivier Baudoin , Antonio M. Echavarren

引用次数: 14