A suspension of the crude 3-methyl-1-(2-methylpropyl)-6-(1-naphthalenylmethyl)-5-[(4-nitrophenyl)thio]thieno[2,3-d]pyrimidine-2,4-(1H, 3H)-dione (Example 35, 1.26 g), iron powder (0.59 g) and ammonium chloride (0.56 g) in ethanol (5 ml) and water (5 ml) was heated at reflux for 4 hours, then cooled to room temperature. Sodium hydroxide solution (10%, 50 ml) was added and the mixture was stirred for 1 hour. The resulting solution was decanted from insoluble solid. The solid and solution were in turn extracted with dichloromethane (3×50 ml) then ethyl acetate (3×50 ml). The combined organic extracts were dried over anhydrous magnesium sulfate, filtered and evaporated under reduced pressure. The residue was partially purified by column chromatography over silica, eluting with ethyl acetate:isohexane (1:1). Some pure material was recrystallised from isohexane: ethyl acetate to give the title compound (0.065 g). The remaining material was purified by preparative normal-phase HPLC with dichloromethane:ethanol gradient elution to give the title compound (0.163 g).
