Polymorphism of Butyl Ester of Oleanolic Acid-The Dominance of Dispersive Interactions over Electrostatic.

Oleanolic (OA) and glycyrrhetinic acids (GE), as well as their derivatives, show a variety of pharmacological properties. Their crystal structures provide valuable information related to the assembly modes of these biologically active compounds. In the known-to-date crystals of OA esters, their 11-oxo derivatives, and GE ester crystals, triterpenes associate, forming different types of ribbons and layers whose construction is based mainly on van der Waals forces and weak C-H···O interactions.

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.

An enantiomerically pure P-stereogenic bisphosphine: (S,S)-ethylenebis[(2-methylphenyl)phenylphosphine] (o-tolyl-DiPAMP).

In connection with a research program involving the synthesis, structure determination, reactivity and ability to coordinate to metal centres of chiral bisphosphine ligands, we have synthesized and structurally characterized, by means of single-crystal X-ray diffraction analysis, the title compound {systematic name: (S,S)-(ethane-1,2-diyl)bis[(2-methylphenyl)phenylphosphane], abbreviated as o-tolyl-DiPAMP}, C28H28P2. So far, neither the free bisphosphine (DiPAMP) nor analogues that incorporate the ethylenebisphosphine frame have had their crystal structures reported. The investigated compound forms crystals which are isostructural with the bisphosphine dioxide analogue [King et al.