Structure and progestational activity of 13-substituted-18-norpregn-4-ene-3, 20-diones, a pilot study

13-Ethyl-18-norpregn-4-ene-3, 20-dione (7) and 13-acetyl-18-norpregn-4-ene-3, 20-dione (4) were synthesized and tested in the s.c. Clauberg assay. The potencies of these compounds (1X and 1/3 X progesterone, respectively) are compared with those reported for 13-vinyl- and 13-cyanomethyl-18-norpregn-4-ene-3, 20-dione. A comparable activity (1/3 X progesterone) was found for 13-acetyl-18-norpregn-4-en-3-one (10) which lacks the 20-carbonyl group.