REGIOSPECIFIC SYNTHESIS OF 4-FLUORO-DELTA(4),3-KETO STEROIDS USING CESIUM FLUOROXYSULFATE

The regiospecific synthesis of two A-ring fluorinated steroids is desc ribed. Treatment of a 4-trimethylstannyl Delta(4),3-keto steroid with caesium fluoroxysulfate gave the corresponding fluorinated steroid in good yield; use of the N-fluorodiazabicyclic reagent, Selectfluor, as the fluorine source provides the same compounds in lower yield. The fl uorination was found to be sufficiently rapid to be potentially useful in the synthesis of F-18 labelled steroids for PETT applications.