estradiol 17β-benzoate estradiol 17β-benzoate estradiol 17β-benzoate (e2-17b) is an estrogen and an estrogen ester—specifically, the c17β benzoate ester of estradiol—which was never marketed. it is the c17β positional isomer of the better-known and clinically used estradiol ester estradiol benzoate (estradiol 3-benzoate; progynon-b). estradiol 17β-benzoate was first described in the 1930s. not to be confused with estradiol benzoate. estradiol 17β-benzoateclinical dataother namese2-17b; zyc30drug classestrogen; estrogen esteridentifiers iupac name phenanthren-17-yl] benzoate cas number983-30-2pubchem cid66420chemspider59794unii3gfx41z289comptox dashboard (epa)dtxsid90243545 chemical and physical dataformulac25h28o3molar mass376.496 g·mol−13d model (jsmol)interactive image smiles c12cc3(1cc2oc(=o)c4=cc=cc=c4)ccc5=c3c=cc(=c5)o inchi inchi=1s/c25h28o3/c1-25-14-13-20-19-10-8-18(26)15-17(19)7-9-21(20)22(25)11-12-23(25)28-24(27)16-5-3-2-4-6-16/h2-6,8,10,15,20-23,26h,7,9,11-14h2,1h3/t20-,21-,22+,23+,25+/m1/s1key:aagoogmsohovse-bzdyccqfsa-n