Mid-infrared (mid-IR) spectroscopy is a powerful tool to study structures of gas-phase molecules and their aggregates at the atomic level. Despite the fact that mid-IR spectroscopy employing linearly-polarized light cannot distinguish between enantiomers of a chiral molecule, it can be used to probe diastereomer specific IR signatures of dimers of chiral molecules depending on whether they comprise homo- or hetero-chiral moieties. Such an approach can potentially be implemented as an analytical tool for analysis of enantiomeric purity of samples. In my presentation I will show results of our recent studies for dimers of simple organic molecules, particularly, amino acids. The results were obtained experimentally employing the CLIO and FELIX free electron lasers as IR light sources in combination with quantum chemical methods.