Removal of the 20-methyl group from 2-methylene-19-nor-(20S)-1α,25-dihydroxyvitamin D3 (2MD) selectively eliminates bone calcium mobilization activity Original Research Article

The 18-nor (7), 21-nor (8) and 18,21-dinor (9) analogs of (20S)-1α,25-dihydroxy-2-methylene-19-norvitamin D3 (6, 2MD) were prepared by convergent syntheses. The known phosphine oxide 10 was coupled by the Wittig–Horner process with the corresponding C,D-fragments (13–15), obtained by a multi-step procedure from commercial vitamin D2. The goal of our studies was to examine the influence of removal of the methyl groups located at carbons 13 and 20 on the biological potency of 2MD in the hope of finding analogs with improved therapeutic profiles.