Estradiol sulfate
As the sodium salt, sodium estradiol sulfate, E2S is present as a minor constituent (0.9%) of conjugated equine estrogens (CEEs), or Premarin. It effectively functions as a prodrug to estradiol in this preparation, similarly to E1S. E2S is also formed as a metabolite of estradiol, as well as of estrone and E1S. Aside from its presence in CEEs, E2S is not available as a commercial pharmaceutical drug.
Cloxestradiol acetate
Cloxestradiol acetate (brand name Genovul), also known as 17-(2,2,2-trichloroethoxy)estradiol "O","O"-diacetate, is a synthetic, steroidal estrogen derived from estradiol. It is the "O","O"-diacetate ester of cloxestradiol, which, in contrast to cloxestradiol acetate, was never marketed.