[3-H-3]Propionic acid (1) was prepared by catalytic hydrogenation of 3-brom
opropionic acid with tritium gas. Fermentations of S. hygroscopicus were tr
eated with 1 to produce [2a,8a,10a,14a-H-3]geldanamycin (2) with a specific
activity df 76.2 mCi/mmol. The effect of the amount of 1 used and the dosi
ng pattern on the specific activity of 2 was investigated.