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Determination of absolute configuration using X-ray diffraction 用x射线衍射测定绝对构型
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.08.018
Simon Parsons
{"title":"Determination of absolute configuration using X-ray diffraction","authors":"Simon Parsons","doi":"10.1016/j.tetasy.2017.08.018","DOIUrl":"10.1016/j.tetasy.2017.08.018","url":null,"abstract":"<div><p>Methods for determination of absolute structure using X-ray crystallography are described, with an emphasis on applications for absolute configuration assignment of enantiopure light-atom organic compounds. The ability to distinguish between alternative absolute structures by X-ray crystallography is the result of a physical phenomenon called resonant scattering, which introduces small deviations from the inherent inversion symmetry of single-crystal X-ray diffraction patterns. The magnitude of the effect depends on the elements present in the crystal and the wavelength of the X-rays used to collect the diffraction data, but it is always very weak for crystals of compounds containing no element heavier than oxygen. The precision of absolute structure determination by conventional least squares refinement appears to be unduly pessimistic for light-atom materials. Recent developments based on Bijvoet differences, quotients and Bayesian statistics enable better and more realistic precision to be obtained. The new methods are sensitive to statistical outliers, and techniques for identifying these are summarised.</p></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.2017.08.018","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73575886","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: 39
Chiroptical spectroscopy and the validation of crystal structure stereochemical assignments 热力光谱学与晶体结构立体化学配位的验证
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.08.019
George E. Tranter, Delphine D. Le Pevelen
{"title":"Chiroptical spectroscopy and the validation of crystal structure stereochemical assignments","authors":"George E. Tranter,&nbsp;Delphine D. Le Pevelen","doi":"10.1016/j.tetasy.2017.08.019","DOIUrl":"10.1016/j.tetasy.2017.08.019","url":null,"abstract":"<div><p><span><span>The absolute stereochemistry of chiral molecules is ideally established to atomic resolution by X-ray crystallographic analysis. However, </span>chiroptical spectroscopies, namely </span>electronic circular dichroism<span><span> (ECD), optical rotatory dispersion<span> (ORD), vibrational circular dichroism (VCD) and </span></span>Raman optical activity<span> (ROA), play important complementary roles in establishing relative and absolute sterochemistries as well as allowing determinations of optical purity. A brief summary of chiroptical spectroscopies is presented, along with guidance to their advantages and disadvantages. The application of ECD to verifying that single crystals selected for crystallographic analysis are indeed representative of bulk material is described.</span></span></p></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.2017.08.019","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88117862","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
Features of electronic circular dichroism and tips for its use in determining absolute configuration 电子圆二色性的特征及其用于确定绝对形状的提示
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.09.015
Jesús T. Vázquez
{"title":"Features of electronic circular dichroism and tips for its use in determining absolute configuration","authors":"Jesús T. Vázquez","doi":"10.1016/j.tetasy.2017.09.015","DOIUrl":"10.1016/j.tetasy.2017.09.015","url":null,"abstract":"<div><p>This review focuses on the general features of electronic circular dichroism<span><span> (ECD) as applied in determining the absolute configuration of organic compounds. The high sensitivity and straightforward spectral interpretation of the </span>exciton<span> chirality method makes this approach very useful, and complementary to X-ray crystallography. A brief tutorial is provided on ECD, with precautions and tips for using it, especially the exciton chirality method. The spectroscopic ECD of several examples are analyzed.</span></span></p></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.2017.09.015","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89091823","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: 19
Determination of the absolute configuration of two αvβ6 integrin inhibitors for the treatment of idiopathic pulmonary fibrosis and investigations on the asymmetric 1,4-addition of arylboronic acids to crotonate esters bearing a C4-oxygen substituent 测定治疗特发性肺纤维化的两种αvβ6整合素抑制剂的绝对构型，并研究芳香硼酸在含有c4 -氧取代基的克罗酮酸酯上的不对称1,4加成
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.08.017
Panayiotis A. Procopiou , Tim N. Barrett , Royston C.B. Copley , Christopher J. Tame
{"title":"Determination of the absolute configuration of two αvβ6 integrin inhibitors for the treatment of idiopathic pulmonary fibrosis and investigations on the asymmetric 1,4-addition of arylboronic acids to crotonate esters bearing a C4-oxygen substituent","authors":"Panayiotis A. Procopiou ,&nbsp;Tim N. Barrett ,&nbsp;Royston C.B. Copley ,&nbsp;Christopher J. Tame","doi":"10.1016/j.tetasy.2017.08.017","DOIUrl":"10.1016/j.tetasy.2017.08.017","url":null,"abstract":"<div><p><span>The absolute configuration of two novel α</span><sub>v</sub>β<sub>6</sub><span><span><span> integrin<span> inhibitors was established via degradation to the corresponding C3-aryl substituted butyrolactone. The configuration of the resulting </span></span>lactones was established by </span>asymmetric synthesis<span><span> using 1,4-addition of arylboronic acids to butenolide, catalysed by bis(norbornadiene)rhodium (I) </span>tetrafluoroborate in the presence of (</span></span><em>R</em><span><span>)-BINAP, and confirmed by X-ray crystallography. Studies on arylboronic acid conjugate additions to acyclic crotonate esters bearing a γ-oxygen substituent are also reported. Three Rh catalysts were investigated and the one giving the highest </span>enantioselectivity was bis(norbornadiene)rhodium (I) tetrafluoroborate.</span></p></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.2017.08.017","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88466303","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
Stereoselective allylation and reduction of N-tert-butanesulfinyl-α-keto aldimines n -叔丁烷磺酸基-α-酮醛胺的立体选择性烯丙基化和还原
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.08.010
Edgar Maciá , Francisco Foubelo , Miguel Yus
{"title":"Stereoselective allylation and reduction of N-tert-butanesulfinyl-α-keto aldimines","authors":"Edgar Maciá ,&nbsp;Francisco Foubelo ,&nbsp;Miguel Yus","doi":"10.1016/j.tetasy.2017.08.010","DOIUrl":"10.1016/j.tetasy.2017.08.010","url":null,"abstract":"<div><p>A simple methodology for the synthesis of <em>N</em>-<em>tert</em><span><span><span><span>-butanesulfinyl-α-keto aldimines from both α-keto aldehydes and </span>carboxylic esters has been developed. The addition of an in situ formed </span>allyl </span>indium<span><span> reagent to these chiral imines was also studied. The addition took place in a sequential manner, first to the imine group with excellent </span>diastereoselectivity<span> and then to the carbonyl group<span> with lower diastereoselectivity. Ruthenium-catalyzed ring closing metathesis of the resulting 5-aminoocta-1,7-dien-4-ol derivatives provided access to 6-aminocyclohex-3-enols. Reduction of the α-keto aldimines led to </span></span></span></span><em>N</em>-<em>tert</em><span>-butanesulfinyl-1,2-aminoalcohols as a 1:1 diastereomeric mixture.</span></p></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.2017.08.010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80919752","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
Influence of solvent polarity on the separation of leucine enantiomers by β-cyclodextrin: a molecular mechanics and dynamics simulation 溶剂极性对β-环糊精分离亮氨酸对映体的影响:分子力学和动力学模拟
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.09.020
Elena Alvira
{"title":"Influence of solvent polarity on the separation of leucine enantiomers by β-cyclodextrin: a molecular mechanics and dynamics simulation","authors":"Elena Alvira","doi":"10.1016/j.tetasy.2017.09.020","DOIUrl":"10.1016/j.tetasy.2017.09.020","url":null,"abstract":"<div><p><span><span><span><span>The interaction between leucine and β-cyclodextrin with different solvents was studied by molecular mechanics and dynamics simulations. In order to analyse the influence of the solvent polarity on the inclusion complex formation and separation process of leucine </span>enantiomers by β-cyclodextrin, the organic modifiers were characterised by the same value of </span>dielectric constant in the electrostatic contribution to the interaction energy, and a different molecular configuration of </span>amino acids<span> (neutral or zwitterion). The complexes formed in polar solvents were more stable than those in non-polar solvents with the same dielectric constant, because the electrostatic contribution is negative for the former and positive for the latter. The optimized structures obtained for leucine enantiomers and β-cyclodextrin in vacuo are non-inclusion complexes. The solvent polarity contributes to increasing the probability of the presence in an inner position for the guest, whereas the results for non-polar configurations were smaller and distributed in larger areas. The regions where the enantiomers spend more time in the simulation correspond to locations with greater chiral discrimination. </span></span><span>d</span>-Leu was the first eluted enantiomer in every case, except for a polar solvent with <span><math><mrow><mi>ε</mi><mo>=</mo><mn>26</mn></mrow></math></span>.</p></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.2017.09.020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80593594","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: 6
Solid state conformations of α,β-unsaturated hydroxamates derived from the ‘chiral Weinreb amide’ auxiliary (S)-N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxylamine 手性Weinreb酰胺辅助物(S)- n -1-(1 ' -萘基)乙基- o -叔丁基羟胺衍生的α，β-不饱和羟酸酯的固态构象
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.07.009
Stephen G. Davies, James A. Lee, Paul M. Roberts, James E. Thomson, Jingda Yin
{"title":"Solid state conformations of α,β-unsaturated hydroxamates derived from the ‘chiral Weinreb amide’ auxiliary (S)-N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxylamine","authors":"Stephen G. Davies,&nbsp;James A. Lee,&nbsp;Paul M. Roberts,&nbsp;James E. Thomson,&nbsp;Jingda Yin","doi":"10.1016/j.tetasy.2017.07.009","DOIUrl":"10.1016/j.tetasy.2017.07.009","url":null,"abstract":"<div><p><span>α,β-Unsaturated hydroxamates derived from the ‘chiral Weinreb amide’ auxiliary (</span><em>S</em>)-<em>N</em>-1-(1′-naphthyl)ethyl-<em>O</em>-<em>tert</em>-butylhydroxylamine consistently adopt a defined conformation and undergo highly diastereoselective conjugate addition reactions with lithium amide reagents. The configuration of the <em>N</em>-1-(1′-naphthyl)ethyl group dictates the position of the <em>O</em>-<em>tert</em><span>-butyl group and also the configuration adopted by the pyramidal nitrogen atom via a ‘chiral relay’ effect. Conjugate addition of lithium amide reagents to these substrates proceeds on the face opposite to both the </span><em>O</em>-<em>tert</em><span>-butyl group and nitrogen lone-pair with high levels of diastereoselectivity.</span></p></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.2017.07.009","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83245881","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: 0
Synthesis, crystal structure, and absolute configuration of the enantiomers of chiral drug xibenolol hydrochloride 手性药物盐酸西贝洛尔对映体的合成、晶体结构和绝对构型
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.08.013
Alexander A. Bredikhin, Zemfira A. Bredikhina, Alexey V. Kurenkov, Aidar T. Gubaidullin
{"title":"Synthesis, crystal structure, and absolute configuration of the enantiomers of chiral drug xibenolol hydrochloride","authors":"Alexander A. Bredikhin,&nbsp;Zemfira A. Bredikhina,&nbsp;Alexey V. Kurenkov,&nbsp;Aidar T. Gubaidullin","doi":"10.1016/j.tetasy.2017.08.013","DOIUrl":"10.1016/j.tetasy.2017.08.013","url":null,"abstract":"<div><p><span>Based on the features of its crystallization, racemic 3-(2,3-dimethylphenoxy)propane-1,2-diol </span><strong>2</strong><span>, the synthetic precursor of the chiral drug xibenolol </span><strong>1</strong><span><span><span>, was resolved into pure </span>enantiomers by the direct method of entrainment. The enantiomers of </span>diol </span><strong>2</strong><span> through a Mitsunobu reaction were converted into the nonracemic 1,2-epoxy-3-(2,3-dimethylphenoxy)propanes (</span><em>S</em>)- and (<em>R</em>)-<strong>3</strong><span>, and then into the xibenolol enantiomers. Single crystals of (+)- and (−)-</span><strong>1</strong>·HCl were studied by X-ray diffraction. On the basis of the Flack parameter, the absolute (<em>R</em>)- and (<em>S</em>)-configurations were assigned to these compounds and to the other intermediate chiral substances.</p></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.2017.08.013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86187353","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: 4
A question of policy: should tests for the self-disproportionation of enantiomers (SDE) be mandatory for reports involving scalemates? 一个政策问题:对映异构体的自歧化(SDE)测试是否应该强制要求涉及缩放的报告?
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.08.020
Vadim A. Soloshonok , Alicja Wzorek , Karel D. Klika
{"title":"A question of policy: should tests for the self-disproportionation of enantiomers (SDE) be mandatory for reports involving scalemates?","authors":"Vadim A. Soloshonok ,&nbsp;Alicja Wzorek ,&nbsp;Karel D. Klika","doi":"10.1016/j.tetasy.2017.08.020","DOIUrl":"10.1016/j.tetasy.2017.08.020","url":null,"abstract":"<div><p><span><span><span>The self-disproportionation of enantiomers (SDE) is a phenomenon that can lead to the perturbation of the enantiomeric excess (ee) in fractions obtained from a scalemic sample that has been subjected to a physical process. While fractional </span>crystallization<span> is widely appreciated as a means to effect enantiopurification, processes that are potentially able to give rise to the SDE phenomenon, notably chromatography, are greatly underappreciated in this regard. In this exposition we question if sufficient care is being taken by workers to avoid the erroneous reporting of stereochemical outcomes in </span></span>asymmetric synthesis, </span>natural products work, and other chiral-based areas of study due to ignorance of the SDE phenomenon and recommend the incorporation of SDE tests via sublimation and achiral chromatography as outlined herein to check for the occurrence of the SDE phenomenon in the applied methodology and routine experimental work.</p></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.2017.08.020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75079690","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: 39
Best practice and pitfalls in absolute structure determination 确定绝对结构的最佳实践和陷阱
Tetrahedron, asymmetry Pub Date : 2017-10-15 DOI: 10.1016/j.tetasy.2017.07.010
Anthony Linden
{"title":"Best practice and pitfalls in absolute structure determination","authors":"Anthony Linden","doi":"10.1016/j.tetasy.2017.07.010","DOIUrl":"10.1016/j.tetasy.2017.07.010","url":null,"abstract":"<div><p>In routine small-molecule single crystal structure determination, accurate absolute structure determination has sometimes been challenging. Developments in diffractometers, X-ray sources, detectors and software, along with new concepts for the elucidation of the absolute structure have seen the greatest advances in recent times. Nonetheless, determining the absolute structure of a crystal, particularly when only light atoms are present, requires some thought in the planning of the experiment in order to obtain the best possible data and some care in modelling the structure and interpreting the results so as not to draw incorrect or unsupported conclusions. Some practical recommendations for best practice and how to avoid pitfalls and misinterpretations are presented as a guide, particularly for those new to the field of crystal structure analysis.</p></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.2017.07.010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77350884","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
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