group on C-8 (A ring) were inactive; (c) oxidation of NCH 2 -7 to an amide group (B ring) caused loss of activity; (d) modification of the C/D ring junction had no effect on activity when the D ring assumed a β configuration whereas a great decrease of activity was observed when that ring assumed an α configuration; (e) selective or complete acetylation of hydroxyl groups of the C ring, epimerization