HIGHLY DIASTEREOSELECTIVE SYNTHESIS OF 11-BETA,17-BETA-DIARYL-18A-HOMO-19-NOR STEROIDS

In a highly diastereoselective fashion novel 11 beta, 17 beta-diaryl s teroids 17 and 18 were synthesized via Birch-type reduction [1] of sty rylic precursors 11 and 15. Both precursors were readily available by Suzuki-type coupling reactions [2] of aromatic boronic acids [3] and t he corresponding enol triflates 6, 10, and 14. Regioselective 17-enol triflate formation in presence of a 11-keto function could be demonstr ated in case of steroid 5. The remarkably high degree of stereoselecti vity observed parallels results from the natural series [4] and demons trated a broader applicability of such single electron transfer reduct ions in stereoselective transformations on the steroid skeleton.