The Preparation of Deuterio Cholesterol*

The study of chemical transformations in the living cell with the aid of the isotope technique requires the preparation of deuterio compounds which contain deuterium atoms linked to carbon atoms. The carbon-deuterium linkages must be stable in the sense that the deuterium atoms will not be replaced by hydrogen atoms on solution in water. In the case of simple organic compounds, standard synthetic procedures will often give the desired compound. The conversion of oleic acid into 9 ,lO-dideuterio stearic acid by the catalytic reduction with deuterium is a simple matter; the preparation of C17D&OOH would obviously be more difficult, as no appropriate hydrogen-free starting substance is available. Its total synthesis from carbon and deuterium, though conceivable, is certainly not practicable. These considerations apply with even greater force to complicated natural products, such as the sterols. Experiments with heavy hydrogen have revealed a new type of chemical reaction, the exchange reaction, which can be utilized for the preparation of deuterio compounds. The general exchange reaction may be written,