Electronic circular dichroism (ECD) and anisotropy spectra carry information on differential absorption of left-and right-circularly polarized light (LCPL and RCPL) by optically active compounds. This makes them powerful tools for the rapid determination of enantiomeric excesses (ee) in asymmetric synthetic and pharmaceutical chemistry, as well as for predicting the ee inducible by ultraviolet (UV) CPL. The ECD response of a chiral molecule is, however, critically dependent on the properties of the surrounding medium. Here, we report on the first ECD/anisotropy spectra of aqueous solutions of the calcium salt dihydrate of glyceric acid. A systematic study of the effect of the salt concentration and pH on the chiroptical response revealed significant changes and the appearance of a new ECD band of opposite sign. Based on the literature, this can be rationalized by the increase in the relative proportion of free glyceric acid/glycerate to Ca 2+ complexes with glycerate with decreasing salt concentration or pH. Glyceric acid can be readily produced under astrophysical conditions. The anisotropy spectra of the solution containing prevalently the free form of this dihydroxy carboxylic acid resemble the ones of previously investigated aliphatic chain hydroxycarboxylic acids and proteinogenic amino acids. This indicates possible common handedness of stellar CPL-induced asymmetry in the potential comonomers of primitive proto-peptides.alkaline earth metal, chiral hydroxycarboxylic acid, circularly polarized light, complexation, CPL scenario, enantiomeric excess, homochirality
| INTRODUCTIONDifferentiation between enantiomers of a chiral species requires a chiral force. Circularly polarized light (CPL) represents a true chiral entity, 1 and the origin of biological homochirality-uniformity of handedness of amino [This article is part of the Special Issue: Chirality in France. See the first articles for this special issue previously published in Volumes 33:9, 33:10, 33:11, 33:12, and 34:1. More special articles will be found in this issue as well as in those to come.]