Difluoroboron complexes as versatile precursors for steroid modification. Lumiestrone-based steroid derivatives: synthesis and structural studies.

A preparation method for steroid-based difluoroboron complexes has been developed using lumiestrone as a steroid example. Previously inaccessible lumiestrone-based difluoroboron complexes annulated at positions 16 and 17 of the D ring have been prepared. Such difluoroboron complexes may have large synthetic potential for heterofunctionalization of steroids at the D ring. An application of a borylation mixture Ac2O-BF3•OEt2 significantly simplify the preparation of steroid "dimers" bearing two estrone moieties connected at positions 2 and 2' via a linker. Crystal structures of key representatives have been determined by X­ray diffraction.