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Methyl esters of [5]‐ladderanoic acid and [3]‐ladderanoic acid were prepared by esterification of the acids isolated from biomass at a wastewater treatment plant. Optical rotations at six different wavelengths (633, 589, 546, 436, 405 and 365 nm) and vibrational circular dichroism (VCD) spectra in the 1800–900 cm⁻¹region were measured in CDCl₃solvent and compared with quantum chemical (QC) predictions using B3LYP functional and 6‐311++G(2d,2p) basis set with polarizing continuum model representing the solvent. QC predictions gave negative optical rotations at all six wavelengths for (R)‐methyl [5]‐ladderanoate and positive optical rotations for (R)‐methyl [3]‐ladderanoate, the same signs as previously reported for the corresponding acids. The crystal structure of (−)‐methyl [5]‐ladderanoate independently confirmed (R) configuration. The QC‐predicted VCD spectra using Boltzmann population weighted spectra of individual conformers did not provide satisfactory quantitative agreement with the experimental VCD spectra. An improved quantitative agreement for VCD spectra could be obtained when conformer populations were optimized to maximize the similarity between experimental and predicted VCD spectra, but more improvements in VCD predictions are needed.

Experimental vibrational Raman and Raman optical activity (ROA) spectra for diacetyl L‐tartaric acid (DAT), two of its esters, namely, monomethyl and lauryl esters (T1OH and T12OH), and corresponding sodium salts (DATNa, T1ONa, and T12ONa), are measured. T12OH and T12ONa represent the first chiral surfactants investigated using ROA spectroscopy. The quantum chemical (QC) predictions using B3LYP functional and 6‐311++G(2d,2p) basis set are used to interpret the ROA spectra for DAT, DATNa, T1OH, and T1ONa. It is found that the use of implicit solvation, as represented in polarizable continuum model (PCM), for predicting the experimental ROA spectra in aqueous solutions is inadequate for DAT and T1OH. However, the same PCM predicts the experimental ROA spectra satisfactorily for the DATNa and T1ONa. This favorable observation for the latter is attributed to the absence of intra‐ and inter‐molecular hydrogen bonding interactions for sodium salts in aqueous solutions. The overwhelming number of conformations resulting from 12‐carbon alkyl chain, in T12OH and T12ONa, makes it impractical to undertake QC predictions for them. Nevertheless, it is found that the predictions made for shorter alkyl chain analogs, namely, T1OH and T1ONa, may be used to explain the experimental ROA spectra of T12OH and T12ONa. The current work highlights the importance of converting carboxylic acids to corresponding sodium salts and of QC predictions for shorter achiral alkyl chain analogs to interpret the ROA spectra of chiral surfactants that contain long achiral alkyl chains.

The importance of the electric‐dipole—electric‐quadrupole polarizability contribution to the vibrational Raman optical activity (VROA) and dimensionless circular intensity difference spectra of (1S)‐camphor is examined. The spectra are simulated with and without this tensor contribution using density functional theory calculations, and similarity is evaluated for each against the experimental spectra. Careful examination of the comparison between experimental and calculated spectra reveals multiple vibrational bands, in the ~1,130–950 cm⁻¹region, originating from −C–H bending vibrations that are dominated by the electric‐dipole—electric‐quadrupole polarizability contributions. The similarity overlap analysis also reveals that the similarity overlap between experimental and predicted spectra in the measured spectral range increases, by up to 12%, when electric‐dipole—electric‐quadrupole polarizability contributions are included. The negative VROA band at 1,125 cm⁻¹in the experimental spectrum of (1S)‐(‐)‐camphor can only be reproduced in the predicted spectra when electric‐dipole—electric‐quadrupole polarizability contribution is included. Investigations on additional molecules indicated that (a) two experimental VROA bands of (1S,4R)‐(+)‐fenchone at ~1,740 and 220 cm⁻¹originate from dominating electric‐dipole—electric‐quadrupole polarizability contribution and (b) the symmetric and antisymmetric ring deformation modes of dimethyloxirane have dominating electric‐dipole—electric‐quadrupole polarizability contribution. These observations establish the importance of electric‐dipole—electric‐quadrupole polarizability contribution to VROA for the first time.

Sesquitepenoids inuloxins A–D, belonging to different subgroups, were isolated fromDittrichia viscosaand showed potential biocontrol of some parasitic plants as Pelipanche, Orobanche, and Cuscuta species. The absolute configurations of the first three inuloxins A–C were previously determined by using experimental and computational chiroptical spectroscopic methods. The absolute configuration of inuloxin D remains to be established. The bioactive inuloxin E, closely related to inuloxin D, was recently isolated from the same plant organic extract. The same relative configuration of inuloxin D was assigned to inuloxin E by comparison of their NMR spectroscopic data. The absolute configurations of inuloxin D and inuloxin E are suggested in this work by analysis of the experimental and predicted chiroptical properties of the 4‐O‐acetyl derivative of inuloxin D.

(R)‐Metacycloprodigiosin can exist in three different tautomeric forms, each with hydrogens at C9′ and C12 insynorantiorientation. With the addition of HCl, this structural diversity reduces tosyn‐(R)‐metacycloprodigiosin‐HCl (1a) andanti‐(R)‐metacycloprodigiosin‐HCl (1b), each with multiple conformers. Energetics and chiroptical properties, namely, electronic circular dichroism (ECD) and specific optical rotation (SOR), of (R)‐metacycloprodigiosin‐HCl have been investigated at B3LYP/6‐311++G(2d,2p) level. The experimental ECD spectra of (R)‐metacycloprodigiosin‐HCl have also been measured. Calculations indicated that the lowest energy conformer of1bis approximately 2.7 kcal/mol lower in energy than that of1a, and the energy barrier forantitosynconversion is approximately 13 kcal/mol. The population weighted calculated SORs of1aand1bare, respectively, positive and negative. The respective calculated ECD spectra of these pseudoenantiomers show an almost mirror image relationship between them. The experimental SOR and ECD compare well with those predicted for1b. Thus,1bis expected to be predominant, a situation confirmed also by nuclear Overhauser effect (NOE) data, with a similar conclusion reached for prodigiosin R1.