C (10)–C (19) bond cleavage reaction of 19-hydroxy-and 19-oxoandrost-4-ene-3, 6, 17- triones (5, 6) was explored under various conditions. Treatment of steroids 5 and 6 with KOH in MeOH gave the A-ring aromatized product 6-oxoestrone (11) in a fair yield, respectively, in contrast, the treatment with a weak base yielded 4-methyl steroid 17 (20%) in the case of 19-alcohol 5 or 19-nor-Δ 5 (10)-steroid 9 (12—67%) along with compound 11 (6—27%) in ...