Synthesis of deuterium- and tritium-labeled 25,26,26,2 6,27,27,27-heptafluorocholesterol

25,26,26,26,27,27,27-Heptafluorocholesterol (F-7-cholesterol) is a novel an alog of cholesterol with potential value in biological investigations. We h ave combined an isotope-labeling strategy described for 15-ketoslerols with modifications in the original synthesis of F-7-cholesterol to prepare anal ogs containing deuterium or tritium at the C-23 position. H-1, H-2, and C-1 3 nuclear magnetic resonance spectra indicated high chemical purity of the deuterium-labeled analog and confirmed the presence of deuterium only at C- 23. The tritium-labeled analog was synthesized in high radiochemical purity with a specific activity of 472 mCi/mmol.