“…The residue, after evaporation of the solvent, was chromatographed on a silica gel column and eluted (gradient) with light petroleum-ether to afford 7a-azido-3,6,11,20-tetruoxopregn-4ene-17a,21-dioZ 21-acetate (18) as an unstable oil (164 mg, 12%), [aID f15"; hmX. 232 nm (E 11 OOO); 6 6.07 (1 H, s, 4-H), 5.90 (1 H, S, 17-OH), 4.87 (2 H, 9, J,,, 18 Hz, 21-H2), 4 C23H29N307 requires C, 60.12; H, 6.36; N, 9.15%; M, 459).…”