5-Cyano-4-(3-methoxyphenyl)-2-methylthio-6-(1,1-bis(ethoxycarbonyl)prop-3-yl)pyrimidine (example 25b, 81 mg) was dissolved in dry CH2Cl2 (1 ml). A 1M solution of tin(IV) chloride in CH2Cl2 (1 ml) was added dropwise and the mixture was stirred at room temperature for 1 h. H2O (10 ml) and EtOAc (10 ml) were then added to the reaction mixture. The organic layer was washed with H2O (10 ml) and sat. aq. NaCl (10 ml), dried (MgSO4) and concentrated under reduced pressure. The title compound was purified by chromatography on silica gel with hept/EtOAc=1/0 to 3/2 (v/v) as eluent.
