High specific activity tritium labeling of vitamin D derivative R0275646

The octahydroindenone intermediate was tritium labeled using T2O isotope exchange labeling, and then elaborated to the vitamin D derivative RO275646. Though this method of labeling was expected to give the minor isomer, it was the shortest and most convenient route to the high specific activity metabolically stable labeled sites. A total of 34 mCi (from two separate runs) at 64 Ci/mmol of [H-3]-RO275646 were prepared by this method. Copyright (c) 2005 John Wiley & Sons, Ltd.