<unk> , also known as 17α-ethynylestradiol or as 17α-ethynylestra-1,3,5(10)-triene-3,17β-diol, is a synthetic estrane steroid and a derivative of estradiol with an ethynyl substitution at the C17α position. The 17α-ethynylation of estradiol to create<unk>  is analogous to the 17α-substitution of testosterone to make testosterone derivatives such as 17α-ethynylated progestins like ethisterone (17α-ethynyltestosterone) and norethisterone (17α-ethynyl-19-nortestosterone) as well as 17α-alkylated androgens/anabolic steroids like methyltestosterone (17α-methyltestosterone). Analogues A number of derivatives of<unk>  exist. These include mestranol <unk>  3-methyl ether), quinestrol <unk>  3-cyclopentyl ether),<unk>  sulfonate <unk>  3-isopropylsulfonate), and moxestrol (11β-methoxy-EE). The former three are prodrugs of<unk> , while the latter one is not. A few analogues of<unk>  with other substitutions at the C17α position exist. Examples include the estradiol derivatives methylestradiol (17α-methylestradiol) and ethylestradiol (17α-ethylestradiol), and the estriol derivatives ethinylestriol (17α-ethynylestriol) and nilestriol (17α-ethynylestriol 3-cyclopentyl ether). Androstane analogues of<unk>  with significant although weak estrogenic activity include ethinylandrostenediol (17α-ethynyl-5-androstenediol), 17α-ethynyl-3β-androstanediol, 17α-ethynyl-3α-androstanediol, and methandriol (17α-methyl-5-androstenediol).
Ethinylestradiol
Vinyltestosterone
Haloprogesterone
Ethyltestosterone
Progestogen
Progestogen 
Methylestradiol
Cloxestradiol acetate