16-SUBSTITUTED STEROIDS

Estriol was originally obtained (1930) by isolation from human pregnancy urine by Marrian (1) and by Doisy et al. (2). Both Doisy (2) and Marrian (3) showed that estriol differed from estrone, another estrogenic hormone occurring in gravid urine, in possessing three acetylizable hydroxyl groups instead of the one hydroxyl and one carbonyl. Butenandt (4) soon (1931) proved that estriol might be regarded empirically as the hydrate of estrone by demonstrating tha.t the trihydroxy estrogen could be dehydrated to produce the ketonic estrogen with the elimination of 1 molecule of water. These findings, therefore, indicated that two of the hydroxyl groups in estriol were vicinal in position and that one of these vi&al hydroxyl groups occupied the same position on the steroid nucleus as that of the carbonyl in estrone. Later researches (5), in which many investigators contributed significant work, served to elucidate fully the correct structural formulas of estrone (I) and estriol (VI).