Towards the Limits of Vibrational Circular Dichroism Spectroscopy: VCD Spectra of Some Alkyl Vinylethers

Zinna, Francesco

doi:10.1002/chir.22555

Cited by 6 publications

(6 citation statements)

References 35 publications

(55 reference statements)

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“…17 The latter technique is particularly useful in the presence of weak or negligible ECD spectra. 18 For both solution ECD and VCD calculations, we first run a thorough conformational analysis with molecular mechanics (Merck Molecular Force Field, MMFF) followed by DFT geometry optimizations; the latter of which was performed firstly at the B3LYP/6-31G(d,p) level and then at the B3LYP/6-311+G(d,p) level. Ten different conformers with a Boltzmann population of 1% at 300K were obtained.…”

Section: Determination Of Absolute Configurationmentioning

confidence: 99%

5- epi -Incensole: synthesis, X-ray crystal structure and absolute configuration by means of ECD and VCD studies in solution and solid state

Avula

Hussain

Csük

et al. 2016

Tetrahedron: Asymmetry

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Incensole (1) and its acetate (2), found in incense, demonstrate interesting biological activities. Incensole acetate (2) was prepared on large-scale employing the Paul and Jauch protocol from the crude extracts of the Boswellia papyrifera Hochst. 5-Epiincensole (3), obtained as colorless crystals, was prepared from incensole acetate via three steps viz., deacetylation, oxidation and reduction. The structure of 5-epi-incensole (3) was elucidated by means of spectroscopic data analysis, and the absolute configuration was established by single crystal X-ray analysis in combination with electronic and vibrational circular dichroism. In particular, applicability of the solidstate ECD/TDDFT protocol to a compound endowed with only two non-conjugated alkene chromophores was verified.

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Section: Determination Of Absolute Configurationmentioning

confidence: 99%

5- epi -Incensole: synthesis, X-ray crystal structure and absolute configuration by means of ECD and VCD studies in solution and solid state

Avula

Hussain

Csük

et al. 2016

Tetrahedron: Asymmetry

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“…The VCD signals appeared in all the investigated region exhibited a vibrational dissymmetry factor (ΔA/A) within the order of 10 −3 to 10 −4 , which satisfied the criterion introduced by Góbi and Magyarfalvi 39 and clearly indicated the reliability of VCD measurement according to the previous study of Zinna and Pescitelli. 40 Overall, VCD study clearly demonstrated that the chirality of alanine at N-terminal determined the stacking chirality of carbonyl groups.…”

Section: Resultsmentioning

confidence: 90%

“…Meanwhile, the spectrum of (L, L)‐ F1 gel also exhibited a negative signal and a positive signal at 1627 and 1635 cm −1 , thus suggesting the carbonyl groups of (L, D)‐ F1 and (L, L)‐ F1 should stack in a left‐handed manner. The VCD signals appeared in all the investigated region exhibited a vibrational dissymmetry factor (ΔA/A) within the order of 10 −3 to 10 −4 , which satisfied the criterion introduced by Góbi and Magyarfalvi and clearly indicated the reliability of VCD measurement according to the previous study of Zinna and Pescitelli . Overall, VCD study clearly demonstrated that the chirality of alanine at N ‐terminal determined the stacking chirality of carbonyl groups.…”

Section: Resultsmentioning

confidence: 97%

Helicity of perfluoroalkyl chains controlled by the self‐assembly of the Ala‐Ala dipeptides

Zhang

Tong

et al. 2019

Chirality

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Four Ala‐Ala dipeptides with a perfluoroalkyl chain at the N‐terminal were synthesized. They were able to self‐assemble into helical nanofibers and/or twisted nanobelts in a mixture of DMSO/H2O. The handedness of nanofibers and nanobelts was controlled by the chirality of the alanine at the N‐terminal. The stacking handedness of the phenylene groups and the helicity of the perfluoroalkyl chain were studied using circular dichroism spectroscopy and vibrational circular dichroism, respectively. The chirality of the alanine at N‐terminal controlled the stacking handedness of the neighboring phenylene groups. Moreover, due to the low potential barrier between M‐ and P‐helices of the perfluorocarbon chain, the handedness of the organic self‐assemblies eventually controlled the helicity of the perfluorocarbon chain. X‐ray diffraction indicated that a lamellar structure was formed by the dimers of the dipeptides.

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“…For the two methods, the common medium is the liquid or solution phase. They are powerful in determining the absolute configurations (ACs), ,,− conformation of molecules, − and intermolecular interactions in solutions. − …”

Section: Introductionmentioning

confidence: 99%

“…However, several problems arise when VOA spectra are modeled. First, reproducing the VOA spectra of a nonrigid molecule requires the proper evaluation of its conformational space, which is a general problem in the study of flexible molecules. − The VCD and ROA spectra are even more conformation-dependent than parent IR and Raman ones. In fact, in classical vibrational spectroscopy, similar modes of different conformers may differ in band intensity and position, yet they can form a common contour.…”

Section: Introductionmentioning

confidence: 99%

Chiral Thiophene Sulfonamide—A Challenge for VOA Calculations

et al. 2017

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Two enantiomers of 2-methyl-N-(1-thien-2-ylethyl)propane-2-sulfonamide (TSA) were synthesized, and their VCD, ROA, IR, and Raman spectra were registered. The solved (S)-TSA X-ray structure shows a disorder connected to the presence of two TSA conformers differing by a slight rotation of the thiophene ring. Two molecules in the unit cell of the monoclinic P2 crystal form a net of NH···OS and C*H···OS hydrogen bonds. Out of a series of computational levels tested to interpret the spectra, the B3LYP functional combined with the def2TZVP basis set satisfactorily reproduces the experimental VCD and ROA spectra. To simulate the VCD spectra of TSA enantiomers in KBr pellets, dimers and tetramers, with two different positions of the thiophene ring, were considered. The VCD spectra measured in CDCl are completely different from those taken in KBr due to the conformational freedom of TSA in chloroform. Seven TSA conformers fall into two groups of opposite configurations at the pyramidal N atom forming the additional stereogenic center. However, the barriers between conformers in each group are lower than the energy of thermal motions at 300 K. Thus, all conformers, but the most stable in each group, are likely to be metastable states. The calculated IR, VCD, Raman, and ROA spectra of the conformers depend not only on the type of stereogenic N atom but also on the thiophene ring rotation. Yet, they are likely to coexist because of low barriers between them. Three approaches were tested to reproduce the chiroptical spectra in solution using PCM and hybrid solvation models. As a consequence, it was found that a model in which all conformers contribute to the spectra with equal population factors seems to best reproduce the experimental data. Such a result suggests that in a dissolved state in 300 K TSA occurs in a very shallow potential well and all of its conformers coexist.

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Towards the Limits of Vibrational Circular Dichroism Spectroscopy: VCD Spectra of Some Alkyl Vinylethers

Cited by 6 publications

References 35 publications

5- epi -Incensole: synthesis, X-ray crystal structure and absolute configuration by means of ECD and VCD studies in solution and solid state

5- epi -Incensole: synthesis, X-ray crystal structure and absolute configuration by means of ECD and VCD studies in solution and solid state

Helicity of perfluoroalkyl chains controlled by the self‐assembly of the Ala‐Ala dipeptides

Chiral Thiophene Sulfonamide—A Challenge for VOA Calculations

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