Pregnenolone-17 α−3H. Synthesis and study of label distribution

Pregnenolone-17α −3H was synthesized by reaction of 17α-bromo-pregnenolone with tritiated acetic acid (CH3CO23H) and zinc metal dust. The distribution of the label in the product was studied; about 98% was at the 17-position and the remainder was randomly distributed on the steroids nucleus. It was also found that when pregnenolone was stirred with deuterated acetic acid (CH3CO22H) and zinc metal dust for a longer period of time (22 hr) and in relatively high concentration, the protons of the C21-methyl group (˜57%) were exchanged for deuterium.