A suspension of 1.0 g of 9-fluoro-11β,16α,17,21-tetra-hydroxy-pregna-1,4-
diene-3,20-dione in a mixture of 35 ml of dioxan, 15 ml of acrolein and 0.1 ml
of perchloric acid was stirred for 3 h at room temperature. The clear solution
thus obtained was poured into an aqueous saturated solution of sodium
bicarbonate. The mixture was extracted twice with benzene, and the benzenic
extract was concentrated to a small volume. The resulting crystals were
collected and the 9-fluoro-11β,21-dihydroxy-16α,17-(2-propenylidenedioxy)-
pregna-1,4-diene-3,20-dione was obtained as white crystals, melting point
200°-205°C.
