Synthesis and in vivo evaluation of 11-substituted estradiol derivatives as anti-implantation agents

Synthesis of 11-substituted estradiol derivatives (12–17) has been carried out by the Grignard reaction with alkyl, allyl, and benzyl halides on 17β-hydroxy-3-methoxy-11-oxo-estra-1,3,5(10),8(9)-tetraene (10). The novel compounds (10 and 12–17) were evaluated for their preliminary post-coital contraceptive (anti-implantation) activity in Sprague–Dawley rats. The tested compounds were administered orally and showed significant anti-implantation activity. Compound 13 is the most potent compound in the series which showed 100% contraceptive efficacy at 1.25 mg kg−1.