Tritiated guanethidine of high specific activity

Due to the desire for biological assay techniques of greater sensitivity and specificity than presently exist for the antihypertensive drug guanethidine, tritium labeled guanethidine of high specific activity was prepared for use in radioimmunoassay procedures. This drug has been labeled in other positions than described here resulting in much lower specific activity and less than optimal sensitivity in RIA work. The work described here involves the preparation, deuteration and tritiation of an olefinic precursor, N-(2-aminoethyl)-Δ4-hexahydroazocine which was converted in one subsequent step to tritiated guanethidine with a specific activity of 72 Ci/mmole (145 mCi/mg) for the sulfate salt and 36 Ci/mmole (182 mCi/mg) for the free base.