• nmr spectroscopy
• enantiomeric excess
• self-aggregation
• dipeptides

The Self-Induced Diastereomeric Anisochrony (SIDA) allows to determine the enantiomeric excess by NMR spectroscopy in a scalemate without the use of a chiral auxiliary. Due to the interactions among enantiomers, diastereomeric complexes may be formed, some peaks may be split, and NMR nonequivalence arise. Several ester derivatives of dipeptides have been studied in order to verify whether they exhibit the SIDA phenomenon or not. These dipeptides were investigated in different solvents so to give the highest possible nonequivalences. Those dipeptides that showed self-discrimination capabilities were then subjected to thermodynamic studies (determination of self-association constants and determination of enthalpy and entropy of self-association), to Diffusion Ordered SpectroscopY (DOSY) experiments and to mono- and bi-dimensional Nuclear Overhauser Effects (NOE) experiments. These measurements allowed to gain insight into the thermodynamic of self-discrimination processes and into the stereochemical arrangements of the supramolecular aggregates responsible for the SIDA phenomenon.