Cyproterone and a comparison with its acetate ester

The crystal structure of cyproterone (systematic name: 6-chloro-1,2-dihydro-17-hydroxy-30H-cyclopropa[a]pregna-1,4,6- triene-3,20-dione), C22H27ClO3, is compared with cyproterone acetate, a potent anti-androgen steroid. The two compounds adopt a similar conformation, except for the cyclopropyl ring attached to the cyclohexenone ring (ring A). Cyproterone further adopts a crystal packing distinct from that of the acetate form. These differences result from hydrogen bonding between the free hydroxy group and the carbonyl group of ring A.