Gari V. Ccana-Ccapatinta , Bruno L. Sampaio , Fernando M. dos Santos Jr. , João M. Batista Jr. , Fernando B. Da Costa
{"title":"由振动圆二色性的咖啡酸酯衍生物的绝对构型分配:氘化的陷阱","authors":"Gari V. Ccana-Ccapatinta , Bruno L. Sampaio , Fernando M. dos Santos Jr. , João M. Batista Jr. , Fernando B. Da Costa","doi":"10.1016/j.tetasy.2017.10.025","DOIUrl":null,"url":null,"abstract":"<div><p><span>Recently, it was observed that infrared (IR) and vibrational circular dichroism<span><span> (VCD) calculations including deuterated hydroxyl groups in phenolic and </span>saccharide moieties improved significantly the agreement with experimental data obtained in methanol-</span></span><em>d</em><sub>4</sub><span><span>. In the present study, the relative and absolute configurations of three methanol-soluble </span>caffeic acid<span> ester derivatives </span></span><strong>1</strong>–<strong>3</strong>, isolated from <em>Tithonia diversifolia</em>, were established by a combined use of experimental and calculated <sup>13</sup><span><span>C NMR chemical shifts, as well as electronic circular dichroism (ECD) and </span>VCD spectroscopies. Interestingly, the attempt to reproduce the deuteration pattern arising from possible isotopic exchange in methanol-</span><em>d</em><sub>4</sub> solution led to nearly mirror image calculated VCD spectra for <strong>1</strong> when compared to the non-deuterated molecule with the same absolute configuration. This latter fact can potentially lead to absolute configuration misassignments. A closer inspection of the vibrational chiroptical properties of <strong>1</strong><span><span> revealed that the deuteration status of the tertiary hydroxyl group at C-2 is critical for the correct reproduction of experimental VCD data in protic solvents. Therefore, in the case of stereochemical analysis of polar chiral </span>natural product molecules, a combination of VCD and ECD is recommended.</span></p></div>","PeriodicalId":22237,"journal":{"name":"Tetrahedron, asymmetry","volume":"28 12","pages":"Pages 1823-1828"},"PeriodicalIF":0.0000,"publicationDate":"2017-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.10.025","citationCount":"10","resultStr":"{\"title\":\"Absolute configuration assignment of caffeic acid ester derivatives from Tithonia diversifolia by vibrational circular dichroism: the pitfalls of deuteration\",\"authors\":\"Gari V. Ccana-Ccapatinta , Bruno L. Sampaio , Fernando M. dos Santos Jr. , João M. Batista Jr. , Fernando B. Da Costa\",\"doi\":\"10.1016/j.tetasy.2017.10.025\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p><span>Recently, it was observed that infrared (IR) and vibrational circular dichroism<span><span> (VCD) calculations including deuterated hydroxyl groups in phenolic and </span>saccharide moieties improved significantly the agreement with experimental data obtained in methanol-</span></span><em>d</em><sub>4</sub><span><span>. In the present study, the relative and absolute configurations of three methanol-soluble </span>caffeic acid<span> ester derivatives </span></span><strong>1</strong>–<strong>3</strong>, isolated from <em>Tithonia diversifolia</em>, were established by a combined use of experimental and calculated <sup>13</sup><span><span>C NMR chemical shifts, as well as electronic circular dichroism (ECD) and </span>VCD spectroscopies. Interestingly, the attempt to reproduce the deuteration pattern arising from possible isotopic exchange in methanol-</span><em>d</em><sub>4</sub> solution led to nearly mirror image calculated VCD spectra for <strong>1</strong> when compared to the non-deuterated molecule with the same absolute configuration. This latter fact can potentially lead to absolute configuration misassignments. A closer inspection of the vibrational chiroptical properties of <strong>1</strong><span><span> revealed that the deuteration status of the tertiary hydroxyl group at C-2 is critical for the correct reproduction of experimental VCD data in protic solvents. Therefore, in the case of stereochemical analysis of polar chiral </span>natural product molecules, a combination of VCD and ECD is recommended.</span></p></div>\",\"PeriodicalId\":22237,\"journal\":{\"name\":\"Tetrahedron, asymmetry\",\"volume\":\"28 12\",\"pages\":\"Pages 1823-1828\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2017-12-15\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://sci-hub-pdf.com/10.1016/j.tetasy.2017.10.025\",\"citationCount\":\"10\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Tetrahedron, asymmetry\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0957416617304688\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"Chemistry\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Tetrahedron, asymmetry","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0957416617304688","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"Chemistry","Score":null,"Total":0}
Absolute configuration assignment of caffeic acid ester derivatives from Tithonia diversifolia by vibrational circular dichroism: the pitfalls of deuteration
Recently, it was observed that infrared (IR) and vibrational circular dichroism (VCD) calculations including deuterated hydroxyl groups in phenolic and saccharide moieties improved significantly the agreement with experimental data obtained in methanol-d4. In the present study, the relative and absolute configurations of three methanol-soluble caffeic acid ester derivatives 1–3, isolated from Tithonia diversifolia, were established by a combined use of experimental and calculated 13C NMR chemical shifts, as well as electronic circular dichroism (ECD) and VCD spectroscopies. Interestingly, the attempt to reproduce the deuteration pattern arising from possible isotopic exchange in methanol-d4 solution led to nearly mirror image calculated VCD spectra for 1 when compared to the non-deuterated molecule with the same absolute configuration. This latter fact can potentially lead to absolute configuration misassignments. A closer inspection of the vibrational chiroptical properties of 1 revealed that the deuteration status of the tertiary hydroxyl group at C-2 is critical for the correct reproduction of experimental VCD data in protic solvents. Therefore, in the case of stereochemical analysis of polar chiral natural product molecules, a combination of VCD and ECD is recommended.
期刊介绍：
Cessation. Tetrahedron: Asymmetry presents experimental or theoretical research results of outstanding significance and timeliness on asymmetry in organic, inorganic, organometallic and physical chemistry, as well as its application to related disciplines, especially bio-organic chemistry.
The journal publishes critical reviews, original research articles and preliminary communications dealing with all aspects of the chemical, physical and theoretical properties of non-racemic organic and inorganic materials and processes. Topics relevant to the journal include: the physico-chemical and biological properties of enantiomers; strategies and methodologies of asymmetric synthesis; resolution; chirality recognition and enhancement; analytical techniques for assessing enantiomeric purity and the unambiguous determination of absolute configuration; and molecular graphics and modelling methods for interpreting and predicting asymmetric phenomena. Papers describing the synthesis or properties of non-racemic molecules will be required to include a separate statement in the form of a Stereochemistry Abstract, for publication in the same issue, of the criteria used for the assignment of configuration and enantiomeric purity.
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