Vibrational Circular Dichroism: Recent Advances for the Assignment of the Absolute Configuration of Natural Products

Burgueño‐Tapia, Eleuterio; Joseph‐Nathan, Pedro

doi:10.1177/1934578x1701200501

Cited by 18 publications

(19 citation statements)

References 67 publications

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“…The method of choice to determine the AC of the ocimene monoterpenoids found in Artemisia absinthium is VCD, which has been used extensively for this group of small terpenoids . Although we had no direct AC determination experience with this type of compound, it turned out from the beginning of this study that, due to their size, these molecules are quite volatile and must therefore be treated accordingly, in particular when recovering samples during the process of going from the initial 1 H NMR spectrum to the VCD measurement, and then back to the 1 H NMR determination, a precautionary routine we always use to be sure the studied compound are stable during the long‐time vibrational optical activity measurements.…”

Section: Resultsmentioning

confidence: 99%

Absolute configuration of the ocimene monoterpenoids from Artemisia absinthium

et al. 2017

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The absolute configuration (AC) of the naturally occurring ocimenes (-)-(3S,5Z)-2,6-dimethyl-2,3-epoxyocta-5,7-diene (1) and (-)-(3S,5Z)-2,6-dimethylocta-5,7-dien-2,3-diol (2), isolated from the essential oils of domesticated specimens of Artemisia absinthium, followed by vibrational circular dichroism (VCD) studies of 1, as well as from the acetonide 3 and the monoacetate 4, both derived from 2, since secondary alcohols are not the best functional groups to be present during VCD studies in solution due to intermolecular associations. The AC follows from comparison of experimental and calculated VCD spectra that were obtained by Density Functional Theory computation at the B3LYP/DGDZVP level of theory. Careful nuclear magnetic resonance (NMR) measurements were compared with literature values, providing for the first time systematic H and C chemical shift data. Regarding homonuclear H coupling constants, after performing a few irradiation experiments that showed the presence of several small long-range interactions, the complete set of coupling constants for 3, which is representative of the four studied molecules, was determined by iterations using the PERCH software. This procedure even allowed assigning the pro-R and pro-S methyl group signals of the two gem-dimethyl groups present in 3.

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Section: Resultsmentioning

confidence: 99%

Absolute configuration of the ocimene monoterpenoids from Artemisia absinthium

et al. 2017

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“…The later technique has shown many advantages for the stereochemical analysis of natural substances since it can be applied in the solution state with the use of rather inexpensive computational calculations. Examples of the use of VCD spectroscopy include many classes of terpenes and alkaloids .…”

Section: Introductionmentioning

confidence: 99%

Enantiomeric high-performance liquid chromatography resolution and absolute configuration of 6β-benzoyloxy-3α-tropanol

2016

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The absolute configuration of the naturally occurring isomers of 6β-benzoyloxy-3α-tropanol (1) has been established by the combined use of chiral high-performance liquid chromatography with electronic circular dichroism detection and optical rotation detection. For this purpose (±)-1, prepared in two steps from racemic 6-hydroxytropinone (4), was subjected to chiral high-performance liquid chromatography with electronic circular dichroism and optical rotation detection allowing the online measurement of both chiroptical properties for each enantiomer, which in turn were compared with the corresponding values obtained from density functional theory calculations. In an independent approach, preparative high-performance liquid chromatography separation using an automatic fraction collector, yielded an enantiopure sample of OR (+)-1 whose vibrational circular dichroism spectrum allowed its absolute configuration assignment when the bands in the 1100-950 cm(-1) region were compared with those of the enantiomers of esters derived from 3α,6β-tropanediol. In addition, an enantiomerically enriched sample of 4, instead of OR (±)-4, was used for the same transformation sequence, whose high-performance liquid chromatography follow-up allowed their spectroscopic correlation. All evidences lead to the OR (+)-(1S,3R,5S,6R) and OR (-)-(1R,3S,5R,6S) absolute configurations, from where it follows that samples of 1 isolated from Knightia strobilina and Erythroxylum zambesiacum have the OR (+)-(1S,3R,5S,6R) absolute configuration, while the sample obtained from E. rotundifolium has the OR (-)-(1R,3S,5R,6S) absolute configuration.

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“…Regarding the AC determination of the sole stereogenic center of 1a by comparison of the experimental and calculated VCD spectra, experience dictates [9,10] that the study of molecules containing alcohols of phenols is not the best idea due to the tendency of these functional groups to associate at least to the solvent, thus providing spectra that are difficult to compare with the calculated ones. An alternative approach to the AC determination would be the study of the molecule by single crystal X-ray diffraction to determine the Flack and Hooft paramenters.…”

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Difficulties to Determine the Absolute Configuration of Guaiaretic Acid

Ortega

Burgueño‐Tapia

Joseph‐Nathan

2018

Natural Product Communications

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An account of the difficulties to determine the absolute configuration (AC) of guaiaretic acid (1a), using contemporary methodology, is described in commemoration of the century of its structure elucidation. In fact, the herein studied molecule was the derived diacetate 1b, since the natural lignan slowly decomposes upon manipulation. Single crystal X-ray diffraction of 1b demonstrated the structure, but calculation of Flack and Hooft parameters to know the AC was unsuccessful since the crystals were triclinic, P-1, which is a centro-symmetric space group. In turn, manual band to band comparison of experimental and DFT B3LYP/DGDZVP calculated VCD spectra of 1b allowed ascertaining its AC, although automatic comparison using the CompareVOA software was not very successful. This behavior is associated to the fact that the studied molecule has a sole stereogenic center located on the acyclic portion of a carbon chain possessing two quite similar substituents. The behavior is discussed in relation to cases where the molecular flexibility also generates a very large number of conformers.

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Vibrational Circular Dichroism: Recent Advances for the Assignment of the Absolute Configuration of Natural Products

Cited by 18 publications

References 67 publications

Absolute configuration of the ocimene monoterpenoids from Artemisia absinthium

Absolute configuration of the ocimene monoterpenoids from Artemisia absinthium

Enantiomeric high-performance liquid chromatography resolution and absolute configuration of 6β-benzoyloxy-3α-tropanol

Difficulties to Determine the Absolute Configuration of Guaiaretic Acid

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