https://chemistry.mdma.ch/hiveboard/rhodium/pdf/archive/merbst/quinoline1999.pdf

Quinoline, quinazoline and acridone alkaloids

In principle, the absolute configuration (AC) of a chiral molecule can be deduced from its optical rotation (OR) and/or its electronic circular dichroism (ECD). In practice, this requires reliable methodologies for predicting OR and ECD. The recent application of ab initio time-dependent density functional theory (TDDFT) to the calculation of transparent spectral region OR and ECD has greatly enhanced the reliability with which these phenomena can be predicted. TDDFT calculations of OR and ECD are being increasingly utilized in determining ACs. Nevertheless, such calculations are not perfect, and as a result, ACs determined are not 100% reliable. In this paper, we examine the reliability of the TDDFT methods in the case of chiral alkenes. Sodium d line specific rotations, [α]D, are predicted for 26 conformationally rigid alkenes of known AC, ranging in size from 5 to 20 C atoms, and with [α]D values in the range of 0−500. The mean absolute deviation of predicted [α]D values from experimental values is 28....

Determination of absolute configuration using density functional theory calculations of optical rotation and electronic circular dichroism: chiral alkenes.

Methodology to calculate electronic chiroptical properties from time-dependent density functional theory (TDDFT) is outlined. Applications of TDDFT to computations of electronic circular dichroism, optical rotation, and optical rotatory dispersion are reviewed. Emphasis is put on publications from 2005 to 2010, but much of the older literature is also cited and discussed. The determination of the absolute configuration of chiral molecules by combined measurements and computations is an important application of TDDFT chiroptical methods and discussed in some detail. Raman optical activity (ROA) spectra are obtained from normal-mode derivatives of the optical rotation tensor and other linear response tensors. A few selected (ROA) benchmarks are reviewed.

Time-Dependent Density Functional Response Theory for Electronic Chiroptical Properties of Chiral Molecules

By reacting flexible and optically transparent in UV−vis molecules such as 1,2-, syn- and anti-1,3-diols, 1,3-sulfanylalcohols of known absolute configuration (AC) with fluorenone dimethyl acetal, the corresponding ketals are obtained. They are conformationally well-defined (only one conformer in most cases) compounds exhibiting medium-high optical rotation (OR) values, which are independent of the solvent, and electronic circular dichroism (ECD) spectra, which show several (up to five) Cotton effects in the 350−200 nm range due to valence shell π→π* transitions. These features allow simulation of the chiroptical properties of these compounds at the TDDFT/B3LYP/6-31G* level of theory to obtain, using the known ACs of these compounds, a satisfactory reproduction of the OR values (sign and order of magnitude; quantitatively, the predicted values are twice the experimental ones), and a more than satisfactory reproduction of the ECD spectra (sign, intensity, and position of the lowest-energy four Cotton effec...

A Chemical/Computational Approach to the Determination of Absolute Configuration of Flexible and Transparent Molecules: Aliphatic Diols As a Case Study

Challenges in the assignment of relative and absolute configurations of complex molecules: computation can resolve conflicts between theory and experiment

The specific rotation of (−)-linarinic acid calculated using Hartree-Fock and density functional theory on 14 representative conformers of this molecule were all negative. The most stable conformer was found to be almost identical to the crystallographic structure. These results are consistent with the assumption that (−)-linarinic acid has a (1S)-configuration. An asymmetric total synthesis with starting products chosen on the basis of the theoretical calculations was found to corroborate the theoretical assignment. On the basis of the theoretical calculations of specific rotations and a total asymmetric synthesis, the absolute configuration of the natural product (−)-linarinic acid was determined to be 1S.

Assignment of the absolute configuration of (-)-linarinic acid by theoretical calculation and asymmetric total synthesis

Assignment of the Absolute Configuration of (-)-Linarinic Acid by Theoretical Calculation and Asymmetric Total Synthesis.

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Assignment of the absolute configuration of (-)-linarinic acid by theoretical calculation and asymmetric total synthesis

Assignment of the Absolute Configuration of (-)-Linarinic Acid by Theoretical Calculation and Asymmetric Total Synthesis.