Hodgkin and C.H. Carlisle determined the crystal structure of cholesteryl iodide, the first completely stereochemically correct steroid structure ever solved.
In 1945, Dorothy Hodgkin and her collaborator C.H. Carlisle reported the crystal structure of cholesteryl iodide, marking the first completely stereochemically correct structural determination of any steroid molecule. Steroids — a class of compounds including cholesterol, sex hormones, and vitamin D derivatives — were of immense interest to chemists and biologists, but their exact three-dimensional shapes had remained elusive and contested.
Using X-ray crystallography, Hodgkin was able to resolve not just the connectivity of atoms in the steroid skeleton but their precise spatial arrangement, settling long-standing debates about steroid stereochemistry. This achievement showcased the extraordinary power of X-ray diffraction techniques to solve problems that had defied conventional organic chemistry methods.
The cholesteryl iodide structure was a crucial proof-of-concept: it demonstrated that Hodgkin's crystallographic methods could resolve complex, biologically important molecules with an accuracy no other technique could match. This success helped establish her reputation as one of the foremost X-ray crystallographers of her generation and paved the way for her subsequent, even more ambitious structural determinations, including penicillin, vitamin B12, and insulin. It stands as one of the pivotal achievements bridging classical organic chemistry and the emerging field of structural molecular biology.