The direction of ionic hydrogenation of estra-1,3,5(10),8,14-pentaenes with triethylsilane in the presence of trifluoroacetic acid is determined by the nature of substituents in the A and B rings. The hydrogenation of 7β-methyl-3-methoxy-D-homo-6-oxaestra-1,3,5(10),8,14-pentaen-17aβ-yl acetate gives mainly 9β-analog, which provides the possibility for synthesizing new inhibitors of enzymes responsible for metabolism of steroidal estrogens.