Crystal structure of rac-(3aR,4S,5aR,6S,9R,10aS,10bR)-3a,5a,9-trimethyltetradecahydro-6,9-epoxycyclohepta[e]inden-4-ol monohydrate

Abstract

The title hydrate, C17H28O2·H2O, was synthesized in order to determine the relative configuration of the tetracyclic framework. The fused 5,6,7-tricarbocyclic core exhibits an entire cis-annulation, featuring a 1,4-cis-relation of the angular methyl groups in the six-membered ring. The oxa bridge of the epoxycycloheptane moiety is oriented towards the concave face of the boat-shaped molecule, whereas the angular methyl groups are directed towards the convex face. The asymmetric unit of the crystal contains two nearly identical formula units, which are related via a pseudo-centre of symmetry. The structure could be solved in the space groups I-4 and I41/a. The refinement in the acentric space group, however, gave significantly better results and these are used in this paper. O—H...O hydrogen bonds are observed between the organic molecules, between the organic molecules and the water molecules, and between the water molecules, forming a chain along the c-axis direction.

Keywords

• crystal structure
• hydrate
• hydrogen bonding
• diterpenoid synthesis