"The Tristeroid"

Trimerization of commercially available coprostanone (a steroid ketone with a cis A/B ring junction) by treatment with titanium tetrachloride yields this unusual, chiral, cleft-containing molecule. Only a single isomer is produced in this triple aldol condensation because the starting material is enantiomerically pure; a racemic ketone would give four isomers. The tristeroid was first synthesized by my student Mary Mathai almost ten years ago, but only in the last year did we obtain crystals suitable for X-ray analysis. The structure is shown below, and for a brief communication describing the synthesis and structure of this molecule see "Trimerization of a Steroid Ketone to Form a Chiral Molecular Cleft," R. A. Pascal, Jr., M. S. Mathai, X. Shen, and D. M. Ho, Angew. Chem. Int. Ed. 2001, 40, 4746-4748.