A process for the conversion of a dimethyl-2H-cyclopenta[a]phenanthren-17(14/f)-one compound of formula (II) into a 10,13- dimethyl-lH-cyclopenta[a]phenanthren-17-yl triflate compound of formula (III): wherein R represents hydrogen or a lower acyl group having 2 to 4 carbon atoms, or a protected derivative thereof the triflating step being conducted in the presence of a base comprising a tertiary or heterocyclic amine selected from the group consisting of pyridine, 2,6-lutidine, N-methylmorpholine, l,4- diazabicyclo[2.2.2]octane (DABCO), trimethylamine, triethylamine, N,N-diisopropylethylamine (DIPEA), quinuclidine and l,8- diazabicyclo[5.4.0]undec-7-ene (DBU).
