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| Other names | 6,8-Didehydroestrone; Estra-1,3,5(10),6,8-pentaen-3-ol-17-one |
| Routes of administration | By mouth |
| Drug class | Estrogen |
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| ECHA InfoCard | 100.007.483 |
| Chemical and physical data | |
| Formula | C18H18O2 |
| Molar mass | 266.340 g·mol−1 |
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Equilenin, also known as6,8-didehydroestrone, as well asestra-1,3,5(10),6,8-pentaen-3-ol-17-one, is anaturally occurringsteroidalestrogen obtained from theurine ofpregnantmares.[1][2] It is used as one of the components inconjugated estrogens (brand name Premarin).[2] It was the first complex natural product to be fully synthesized, in work reported by 1940 byBachmann andWilds.[3]
The synthesis developed by theBachmann group started from Butenand's ketone[4] – the 7-methoxystructural analog of1,2,3,4-tetrahydrophenanthren-1-one[5] – and which can be readily prepared from 1,6-Cleve's acid.[6] The approach was based on well-established transformations like theClaisen condensation, theReformatsky reaction, theArndt–Eistert reaction, and theDieckmann condensation.[3]Nicolaou described this preparation as ending the era preceding the post-World War II work ofRobert Burns Woodward that introducedenantioselective synthesis;[4] in this synthesis, a mixture of stereoisomers were prepared and thenresolved,[6] and the choice of target was partly because of the existence of only two chiral carbons and hence only four stereoisomers.[5]
The overall yield of the synthesis was 2.7% based on a twenty-step process starting from Cleve's acid.[6]