The disordered structure of sparsentan: energy calculations for competing chain conformations.

The crystalline form of sparsentan (SST) (systematic name: 2-{4-[(2-butyl-4-oxo-1,3-diazaspiro[4.4]non-1-en-3-yl)methyl]-2-(ethoxymethyl)phenyl}-N-(4,5-dimethyl-1,2-oxazol-3-yl)benzenesulfonamide), CHNOS, was produced and characterized using single-crystal and powder X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and IR spectroscopy. The SST molecule displays positional disorder in three different sections. Viability tests of alternative disorder models involved the calculation of energetic contributions to analyse each possible molecular conformation within its crystal environment and identify the energetically most favourable conformations in the lattice.