Structure of Calciferol

Abstract

FOR some time it has appeared very desirable to undertake, for a calciferol derivative, a detailed X-ray analysis similar to that achieved for cholesteryl iodide¹. Such an analysis should settle once for all many doubtful points in sterol chemistry and, incidentally, resolve the conflict between the early crystallographic and chemical evidence on the structure of calciferol². The X-ray analysis of cholesteryl iodide was possible owing to the presence of the heavy iodine atom in the molecule, which permitted the direct calculation of electron-density projections. In the case of calciferol, our chief difficulty has been in finding any crystalline heavy-atom derivative. Dr. and Mrs. Cornforth were finally successful in preparing for us crystals of calciferol-4-iodo-5-nitro-benzoate, and from these we have now obtained evidence, by X-ray analysis, on the molecular structure of calciferol.