1/21/2024 0 Comments Elucidate ai![]() According to the researchers, their approach is quite general and applicable to the analysis of any type of molecular spectra. The paper shows how the novel ‘AI toolbox’ leads to reliable assignments of absolute configuration and provides insight into conformational heterogeneities - even for difficult molecules that are flexible and feature a large number of chiral centres. It also identifies on-the-fly when a given chiroptical technique is not able to make any reliable conformational predictions. The second is a hierarchical clustering algorithm that analyses the trends in the spectra of the considered conformations. The first is a genetic algorithm that explicitly takes the uncertainties in the computed energies into account in the comparison between experimental and predicted spectra to help identify the most relevant conformations out of all possible conformations. They present an elaborate protocol that combines two artificial intelligence (AI) algorithms. In their Angewandte paper, the researchers describe how the strategic use of artificial intelligence helps to overcome this impasse. ![]() Reliable assignment of absolute configuration The larger the number of chiral centres and the larger the conformational flexibility, the poorer the quality -if not impossibility- of the stereochemical determination. As there is an intrinsic uncertainty in these energies, there can be a large variation in simulated spectra. And here comes the snag, because this average critically depends on the energies of these conformers. More important is that for such a comparison an average needs to be taken over all possible conformations the molecule can adopt. For one thing, the simulation can become time-consuming and expensive. The latter can be generated for example using Density Functional Theory (DFT), but in particular for complex molecules this has serious limitations. However, to derive an absolute configuration from a recorded spectrum, a comparison with simulated spectra is needed. This is unique for each molecule and can even distinguish the mirror image of the same molecule. Techniques such as electronic circular dichroism (ECD), vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectroscopy apply such light to yield a spectroscopic fingerprint. The common approach is to use circularly polarized light that in itself displays chirality: its circular polarization can be left or right. Artificial intelligence helps elucidate the precise spatial structure of complex chiral moleculesĭetermining the precise spatial structure of a chiral molecule, the absolute configuration, is far from easy. ![]()
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