FACIAL SELECTIVITY IN THE HYDROBORATION OF ANDROST-4-ENES

In the absence of an allylic hydroxy group, the stereochemistry of hyd roboration of an androst-4-ene is determined by the presence and stere ochemistry of the C-10 methyl group, Allylic hydroxy groups at C-3 dir ect the hydroboration/oxidation to the anti-face. In the ase of the 3 alpha-alcohol, this effect is in opposition to the normal hydration fr om the alpha-face of the steroid and leads to the 4 beta-alcohol. The stereochemistry of 4 beta,17 beta-diacetoxy-19-nor-5 beta-androstane w as established by X-ray crystallography.