An efficient synthesis of 3-methoxy-19-norpregna-1,3,5(10),16-tetraen-20-one

An efficient preparative method for the synthesis of 3-methoxy-19-norpregna-1,3,5(10), 16-tetraen-20-one was suggested. This compound is a key intermediate product in the preparation of 3,20-dihydroxy-19-norpregnatrienes, antagonists of estrogen receptor and cytotoxic agents. The reaction of 16-dehydro-17-carbonitrile (obtained in two steps from estrone methyl ether) with methyl magnesium halides gave the target product in high yield. While studying this reaction, we isolated and characterized an unusual steroid dimer, a fused 16,17-pyridinosteroid substituted in the hetero ring of the second steroid molecule. A mechanism of its formation was suggested.