Hydrogen-bonded aggregations of oxo-cholic acids

Abstract

The crystal structures of six new crystals of oxo-cholic acids (oxo-CA) are reported: (I) 3α,12α-dihydroxy-7-oxo-5β-cholan-24-oic acid; (II) 3α,7α-dihydroxy-12-oxo-5β-cholan-24-oic acid; (III) 7α-hydroxy-3,12-dioxo-5β-cholan-24-oic acid; (IV-α) and (IV-β) 12α-hydroxy-3,7-dioxo-5β-cholan-24-oic acid; (V) 3,7,12-trihydroxy-5β-cholan-24-oic acid. (IV-β) is a pseudopolymorphic solvated form of (IV-α) and contains small channels which can trap disordered water molecules. In all the structures the four saturated cycles, forming the common alicyclic skeleton, have the same conformation, while the carboxylic side chain adopts flexible conformations in order to produce the most efficient crystal aggregations. The structures display a variety of supramolecular architectures dominated by networks of cooperative O—H...O hydrogen bonds forming different packing motifs often supported by weaker C—H...O interactions.