The oxidation of PGF2alpha with 2,3-dichloro-5,6-dicyanobenzoquinone gives 15-keto-PGF2alpha (I), which is silylated as usual with TMSCl to the tris-trimethylsilyl derivative (II). The normal methylation of (II) with methylmagnesium bromide followed by hydrolysis yields the 15-methyl PGF2alpha (IIIa-b), which is then methylated with diazomethane to the 15-methyl PGF2alpha methyl ester (IV). The selective silylation of 15-methyl PGF2alpha methyl ester (IV) at C-11 with an excess of trimethylsilyldiethylamine (A) in acetone at -45 C gives the monotrimethylsilyl derivative (V), m.p. 33-5 C, which is oxidized with CrO3-dipyridine in pyridine to the ketone (VI) and finally hydrolyzed with aqueous methanol and a small amount of acetic acid to the 15-methyl PGE2 methyl ester.