To 1,6-dihydro-1-(2-methoxyethyl)-6-oxo-2-(3-thienyl)-5-pyrimidinecarboxylic acid (i.e. the product from Example 10, Step C) (0.5 g, 1.8 mmol) in 10 mL of dichloromethane was added oxalyl chloride (0.45 g, 3.6 mmol) and one drop of N,N-dimethylformamide. The reaction mixture was stirred at room temperature for 2 h and then concentrated under reduced pressure. The crude oil was redissolved in 10 mL of dichloromethane and treated with 1,3-cyclohexanedione (0.22 g, 2.0 mmol) and triethylamine (0.18 g, 1.8 mmol). The reaction mixture was stirred for 30 min then treated with a catalytic amount of 2-hydroxy-2-methyl-propanenitrile (0.015 g, 0.18 mmol) and triethylamine (0.182 g, 1.8 mmol) and stirred at ambient temperature for 16 h. The reaction mixture was then concentrated under reduced pressure and purified by medium pressure liquid chromatography on silica gel eluting with 0 to 10% methanol in chloroform to provide 0.160 g of the title compound (also known as 2-[[1,6-dihydro-1-(2-methoxyethyl)-6-oxo-2-(3-thienyl)-5-pyrimidinyl]carbonyl]-1,3-cyclohexanedione), a compound of the invention, as a solid.
