estradiol mustard estradiol mustard estradiol mustard, also known as chlorphenacyl estradiol diester, as well as estradiol 3,17β-bis(4-(bis(2-chloroethyl)amino)phenyl)acetate, is a synthetic, steroidal estrogen and cytostatic antineoplastic agent and a chlorphenacyl nitrogen mustard-coupled estrogen ester that was never marketed. it is selectively distributed into estrogen receptor (er)-positive tissues such as er-expressing tumors like those seen in breast and prostate cancers. for this reason, estradiol mustard and other cytostatic-linked estrogens like estramustine phosphate have reduced toxicity relative to non-linked nitrogen mustard cytostatic antineoplastic agents. however, they may stimulate breast tumor growth due to their inherent estrogenic activity and are said to be devoid of major therapeutic efficacy in breast cancer, although estramustine phosphate has been approved for and is used (almost exclusively) in the treatment of prostate cancer. estradiol mustardclinical dataother namesnsc-112259; chlorphenacyl estradiol diester; estradiol 3,17β-bis(4-(bis(2-chloroethyl)amino)phenyl)acetatedrug classchemotherapeutic agent; estrogen; estrogen esteridentifiers iupac name phenyl]acetyl]oxy-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopentaphenanthren-17-yl] 2-phenyl]acetate cas number22966-79-6pubchem cid31586chemspider29294uniigeo3f3a4k1chebichebi:82520chemblchembl1697793comptox dashboard (epa)dtxsid5020574 chemical and physical dataformulac42h50cl4n2o4molar mass788.67 g·mol−13d model (jsmol)interactive image smiles c12cc3(1cc2oc(=o)cc4=cc=c(c=c4)n(cccl)cccl)ccc5=c3c=cc(=c5)oc(=o)cc6=cc=c(c=c6)n(cccl)cccl inchi inchi=1s/c42h50cl4n2o4/c1-42-17-16-36-35-13-11-34(51-40(49)26-29-2-7-32(8-3-29)47(22-18-43)23-19-44)28-31(35)6-12-37(36)38(42)14-15-39(42)52-41(50)27-30-4-9-33(10-5-30)48(24-20-45)25-21-46/h2-5,7-11,13,28,36-39h,6,12,14-27h2,1h3/t36-,37-,38+,39+,42+/m1/s1key:lrsfxijghrpoqq-vzrqqipssa-n