Reaction of androst-5-en-17-one with hypobromous acid and its use for synthesis of 19-oxygenated 5-ene and 4-en-6-one steroids.

Reaction of androst-5-en-17-one (1) with hypobromous acid using a short reaction time (30 min) along with a careful isolation procedure gave, for the first time, the addition product, 5 alpha-bromo-6 beta-hydroxyandrostan-17-one (3), in 43% yield. This bromohydrin was much more reactive than 5 alpha-bromo-3 beta-acetoxy-6 beta-hydroxyandrostan-17-one (4) towards KHCO3 and HClO4. The high reactivity of compound 3 was found to be a principal reason for the difficulty in isolating this compound by the addition reaction so far. 19-Hydroxyandrost-5-en-17-one (16) and androst-5-ene-17,19-dione (18), as well as 19-hydroxyandrost-4-ene-6,17-dione (28) and androst-4-ene-6,17,19-trione (29), were synthesized through hypoiodite reaction of the bromohydrin 3 as a key reaction.