Optically pure 2-(fluoromethyl)-2-[(4-methylphenylsulphinyl)methyl]oxirane has been obtained in good yield and with high d.e. by reacting diazomethane with optically pure 1-fluoro-3-(4-methylphenylsulphinyl)propan-2-one. Regio- and stereo-selective openings of oxirane ring performed with selected nucleophiles afforded several useful derivatives.