Insights into isostructural and non-isostructural crystals of esters of oleanolic acid and its 11-oxo derivatives.

Synthesis and structural characterization of new esters of oleanolic acid and its 11-oxo derivatives are reported. Compounds crystallize in four isostructural groups, each containing one to four structures. Single-crystal X-ray analysis revealed that molecules belonging to non-isostructural groups self-associate according to two schemes that describe also supramolecular architectures in crystals of glycyrrhetinic acid derivatives. Structural motifs arise as a result of van der Waals forces. Parameters introduced for the analysis of one- and two-dimensional assemblies allow the comparison of motifs in isostructural and non-isostructural crystals, including polymorphs, and a qualitative assessment of differences in molecular self-assembly. One-, two- or three-dimensional similarity has been confirmed by XPac calculations.