65 s 3h 3 u03b1 oh 5 u03b1 pregnan 20 one 3 mmol was dissolved in 20 ml dry dichloromethane under n 2 atmosphere dast 700 mg 4 33 mmol was added slowly dropwise at u2212 78 u00b0 c and the resulting yellowish solution was left stirring at rt for 1 h reaction was followed by tlc the solution was quenched by careful addition of a 5 nahco 3 solution 60 ml the water phase was extracted with dichloromethane 3 u00d7 20 ml the organic phases collected dried over mgso 4 and the solvent removed under reduced pressure yielding a yellowish oil which was purified by silica flash column chromatography pentane ethyl acetate 9 1 products are in the order elimination of h 2 o at 2 3 positions yield 67 fluorination at 3 oh with inversion of configuration 30 fluorination at 3 oh with retention of configuration 3 traces 1 h nmr 400 mhz cdcl 3 d6 u03b4 4 87 4 75 d 1h 2 53 t 1h 2 11 s 3h 2 00 m 1h 0 95 m 1h 0 80 m 1h 0 78 s 3h 0 60 s 3h 3 u03b1 fluor 5 u03b1 pregnan 20 one 10 mmol is dissolved in dichloromethane 5 ml and ethanol 50 ml at rt and air atmosphere in a 250 ml round bottom flask 4 equiv of nh 2 oh chlorhydrate and 4 equiv of sodium acetate are dissolved in 5 ml h 2 o and then added to the steroid solution 20 ml of ethanol are added and the mixture put.