segesterone segesterone segesterone (inn, usan), also known as 17α-hydroxy-16-methylene-19-norprogesterone or as 17α-deacetylnestorone, is a steroidal progestin of the 19-norprogesterone group that was never marketed. an acetate ester, segesterone acetate, better known as nestorone or elcometrine, is marketed for clinical use. segesterone acetate produces segesterone as a metabolite. this article is about a non-clinically used progestin compound. for the pharmaceutical drug, see segesterone acetate. segesteroneclinical dataother names17α-hydroxy-16-methylene-19-norprogesterone; 16-methylene-17α-hydroxy-19-norpregn-4-ene-3,20-dione; 17α-deacetylnestoroneidentifiers iupac name (8r,9s,10r,13s,14s,17r)-17-acetyl-17-hydroxy-13-methyl-16-methylidene-2,6,7,8,9,10,11,12,14,15-decahydro-1h-cyclopentaphenanthren-3-one cas number7690-08-6pubchem cid11823650chemspider9998301unii09q5uv3747keggd10987chemblchembl2107778comptox dashboard (epa)dtxsid00998190 chemical and physical dataformulac21h28o3molar mass328.452 g·mol−13d model (jsmol)interactive image smiles cc(=o)c1(c(=c)cc2c1(ccc3c2ccc4=cc(=o)ccc34)c)o inchi inchi=inchi=1s/c21h28o3/c1-12-10-19-18-6-4-14-11-15(23)5-7-16(14)17(18)8-9-20(19,3)21(12,24)13(2)22/h11,16-19,24h,1,4-10h2,2-3h3/t16-,17+,18+,19-,20-,21-/m0/s1key:sflxyfzgksgfka-xudstzeesa-n