Add time:09/26/2019         Source:sciencedirect.com

All four diasteromeric 16,17-diols in the 3-methoxy-13α-estra-1,3,5(10)-triene series have been synthesized. The trans-diols 1 and 2 can be obtained by hydroborating the 17-enol acetate 6 (61%, ratio 27:73, preferred α attack). OsO4 dihydroxylation of the olefin 7 yielded the cis-diols 3 and 4 (ratio 13:87). The dihydroxylation proceeds with preference for β attack caused by a C-ring twist-boat form of 7. The conformations of the diols 2 and 4, the 17-benzyl-17-hydroxy compounds 9 and 10 (obtained by Grignard reaction), and the 16α-bromo-17β-hydroxy compound 8 were determined by X-ray analysis and by 1H NMR spectroscopy in solution. Some compounds, in spite of a 17β-hydroxy group, had a conformation with a ring C chair form (4, 8, 9) caused by intermolecular interaction in the solid state. The rest of the compounds studied here (2, 10) possessed a conformation with a ring C twist-boat form, which has been also found for all 17β-substituted compounds in solution. The preferred conformation of the D-ring with 17β-substituents seems to be the 16β-envelope form or near this form, but the existence of the 16α-envelope form (inversion of the ring D) for some compounds showed great variance in the conformation of ring D, which is substituent dependent.

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