Prepared according to the procedure described in Example 5 from n-butyllithium (2.0M solution in hexanes, 0.32 ml) and diisopropylamine (0.093 ml) in anhydrous tetrahydrofuran (5 ml), 3-methyl-1-(2-methylpropyl)-6-(1-naphthalenylmethyl)thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione (0.20 g) in anhydrous tetrahydrofuran (5 ml) and 3-{[dimethyl(1,1-dimethylethyl)silyl]oxy}propyl 4-methylphenylthiosulfonate (0.19 g, J. Med. Chem. 1995, 38, 2557) in anhydrous tetrahydrofuran (2 ml). The crude adduct was dissolved in tetrahydrofuran (6 ml) and treated with tetrabutylammonium fluoride hydrate (0.20 g). After 16 hours, the solution was diluted with water (30 ml) and extracted with ether (2×30 ml). The organic extracts were dried over anhydrous magnesium sulfate, filtered and evaporated under reduced pressure. The residue was purified by column chromatography over silica, eluting with ether and was then recrystallised from ethyl acetate/hexane to give the title compound (0.098 g).
