fenestrel fenestrel fenestrel (inn, usan) (developmental code name orf-3858) is a synthetic, nonsteroidal estrogen that was developed as a postcoital contraceptive in the 1960s but was never marketed. synthesized by ortho pharmaceutical in 1961 and studied extensively, it was coined the "morning-after-pill" or "postcoital antifertility agent". fenestrel is a seco analogue of doisynolic acid, and a member of the cyclohexenecarboxylic acid series of estrogens. not to be confused with phenestrol or fosfestrol. fenestrelclinical dataother namesdemethoxycarbestrol; nsc-86465; 2-methyl-3-ethyl-4-phenyl-δ4-cyclohexenecarboxylic acidatc codenoneidentifiers iupac name 5-ethyl-6-methyl-4-phenylcyclohex-3-ene-1-carboxylic acid cas number7698-97-7pubchem cid24371chemspider22786uniilec4215v9rchemical and physical dataformulac16h20o2molar mass244.334 g·mol−13d model (jsmol)interactive image smiles ccc1c(c(cc=c1c2=cc=cc=c2)c(=o)o)c inchi inchi=1s/c16h20o2/c1-3-13-11(2)14(16(17)18)9-10-15(13)12-7-5-4-6-8-12/h4-8,10-11,13-14h,3,9h2,1-2h3,(h,17,18)key:clmfexdzpbgyqq-uhfffaoysa-n