Assignment of the Absolute Configurations of Natural Products by Means of Solid‐State Electronic Circular Dichroism and Quantum Mechanical Calculations

Solid‐state Circular Dichroism and Hydrogen Bonding, Part 2: The Case of Hypothemycin Re‐investigated

“…42,47,48,51,71 A convincing argument is provided by the comparison between the results obtained for hypothemycin (1) and massarigenin A (2): for 1, hydrogen bonds are at least as important as intermolecular exciton couplings in determining the solid-state CD spectrum; for 2, the latter interactions surpass the former. A survey of published data reveals in fact no clear-cut relation between the appearance of intrinsic solid-state signals and either the molecular structure or the crystal space group.…”

“…42,48 In these latter, however, very less expensive semi-empirical methods (CNDO or ZINDO) were used for CD calculations. 42,48 In these latter, however, very less expensive semi-empirical methods (CNDO or ZINDO) were used for CD calculations.…”

“…In fact, all conformers with significant population contribute to the observed CD spectrum. 7,[42][43][44][45] The use of the solid-state approach has a twofold beneficial impact on the generation of input structure: first, the conformational analysis and geometry optimization(s) are skipped; second, the geometry responsible for the experimental spectrum is exactly the same of that employed in the calculations. 40 In the solid crystalline state, on the contrary, a single, fixed conformation is normally observed (provided that polymorphism is excluded), and such a geometry is possibly determined by X-ray analysis.…”

Cis‐Diastereoselectivity in Pictet–Spengler Reactions of L‐Tryptophan and Electronic Circular Dichroism Studies

“…ECD measurements are corroborated by circular dichroism calculations run with the time‐dependent density functional theory (TDDFT) method . In particular, X‐ray geometries were employed as the main input structures for TDDFT calculations, according to the so‐called solid‐state ECD TDDFT approach …”

Structural, spectroscopic, and computational characterization of the cleavage product of dimolybdenum(II) core under aerobic conditions

“…Figure 10B shows the comparison of the experimental solidstate ECD and UV-vis spectra of 2 with curves simulated by TDDFT calculations based on the geometry adapted from the X-ray structure. Such a methodology, known as solid-state CD/TDDFT, was currently developed 34 and applied intensively in the field of natural and synthetic products by many authors, [35][36][37][38] mostly due to the advantage of making the conformational analysis step unnecessary. The TDDFT calculations in our case were performed in a vacuum only at B3LYP/6-311++G(d,p) for C, H, and O atoms and B3LYP/LanL2DZ for Mo atom level of theory since our previous work 2 demonstrated the effectiveness of this combination of basis sets in similar systems containing molybdenum atoms.…”