n-Butyllithium (19.2 ml of a 2.5M solution in hexane) was added dropwise to a stirred suspension of the product of stage (a) above (5.0 g) in dry tetrahydrofuran (100 ml) under nitrogen at -70° C. The mixture was stirred at -70° C. for 20 minutes and then at 5° C. for 3 hours. It was then cooled to -70° C. and treated with 4,6-dimethoxy-2-methylsulfonylpyrimidine (5.42 g), and the mixture was stirred at -70° C. for 1 hour, then at room temperature overnight. Saturated ammonium chloride solution (500 ml) was added, and the mixture was extracted with ethyl acetate (2×100 ml). The combined extracts were washed with saturated sodium chloride solution (50 ml), dried and evaporated to give an orange oil which was triturated with hexane to give 5.35 g of the desired product as a pale yellow solid, mp 89°-92° C.
