Homochiral vs. heterochiral sodium core dimers of tartaric acid esters: A mass spectrometry and vibrational spectroscopy study

Abstract

The mixed sodium core dimers of dimethyl-L-tartrate (Lmt) and the two enantiomers of diisopropyl tartrate (Lipt and Dipt) are studied by mass spectrometry coupled with laser vibrational spectroscopy. Infra-Red Multiple Photon Dissociation (IRMPD) spectra of the two diastereomer sodium-core dimers, namely, LmtLiptNa + and LmtDiptNa + , are identical in the fingerprint region but show a slight difference in the OH stretch region. Comparison to ab initio calculations indicates that the formed complexes probably reflect the structures preexisting in solution. The difference between LmtLiptNa + and LmtDiptNa + arises from the presence of an additional Na + …O interactions in the homochiral complex. The two complexes also differ in the strength and nature of the OH…OC hydrogen bond. Highlights:  Sodium ion-core dimers of tartaric acid esters are studied by mass spectrometry and laser spectroscopy  Infra-red Multiple photon spectroscopy coupled with quantum chemical calculations aim at explaining the chirality effects observed in these systems. 2  Infra-red spectroscopy shows that the dimer with two monomers of identical absolute configuration possesses one more hydrogen bond relative to the heterochiral dimer.

Application of Infrared Multiple Photon Dissociation (IRMPD) Spectroscopy in Chiral Analysis

“…Barbu-Debus et al studied the homochiral and heterochiral sodium core dimers of tartaric acid esters [57]. The dimers of dimethyl-L-tartrate (Lmt) and the two enantiomers of diisopropyl tartrate (Lipt and Dipt) are generated by ESI and studied by IRMPD method in both fingerprint and 3 µm regions.…”

Homochiral vs. heterochiral preference in chiral self-recognition of cyclic diols

“…The heterochiral dimer shows more conformational flexibility than the homochiral one as it exists in two forms. A larger conformational flexibility has been observed already for the less stable configuration of chiral systems, for example heterochiral peptides, or protonated methyl tartrate dimers, 52,62,63 or the homochiral 1-indanol dimer. 11 A larger conformational flexibility of the homochiral adduct was observed as well for the trans -CD dimer for which the most stable calculated dimer is heterochiral.…”

How change in chirality prevents β-amyloid type interaction in a protonated cyclic dipeptide dimer

“…84 They also show much more specificity than chiral amino acids 85 like glutamic acid dimers or other simple systems like sodium core methyl tartrate dimers, although the latter display the multiple interaction points that are thought to be necessary for chiral recognition. 86 This selectivity probably arises partially from the diastereomerism being intramolecular in nature, in contrast to the diastereomeric complexes mentioned above, which might result in stronger effects due to reduced flexibility. 61 This may also be due to the peculiar properties of histidine.…”