16α-Hydroxyfriedelin and 3-Oxo-16-methylfriedel-16-ene as Building Blocks: Crystal Structure and Hirshfeld Surfaces Decoding Intermolecular Contacts

Abstract

In this paper the importance of C–H⋯O intermolecular hydrogen bonds and van der Waals forces in crystal packing stabilization of 16α-hydroxyfriedelin (1) and 3-oxo-16-methylfriedel-16-ene (2) is described. Compound 1 is a natural product isolated from the hexane extract of Salacia elliptica branches, whereas compound 2 is obtained from compound 1 after dehydration accompanied by methyl migration of C-17 to C-16. The single-crystal X-ray diffraction experiments for 1 and 2 were carried out at 150 K, and the crystallographic study demonstrated that these compounds crystallize in noncentrosymmetric space groups, with 1 showing an orthorhombic P212121 space group and 2 a monoclinic P21 one. Compounds 1 and 2 are composed of five fused six-membered rings presenting a chair conformation, except for the central ring of 2, which adopts a half-chair conformation. In addition, the intra- and intermolecular parameters were studied using CCDC MOGUL analyses and Hirshfeld surfaces.