2-Iodopropane (0.1 ml) and potassium carbonate (100 mg) were added to a solution of 6-[(3,5-dimethyl-1H-pyrazol-4-yl)methyl]-5-[(4S)-4-hydroxyisoxazolidin-2-ylcarbonyl]-1-(isobutyl)-3-methylthieno[2,3-d]pyrimidine-2,4(1H,3H)-dione (example 11, 100 mg) in dimethylformamide (1 ml) and the mixture stirred at 100° C. After 2 hours, further 2-iodopropane (0.2 ml) and potassium carbonate (200 mg) were added. After a further 16 hours, the mixture was cooled to room temperature, diluted with water (20 ml) and extracted with ethyl acetate (2×20 ml). Combined organic extracts were treated with pyrrolidine (0.1 ml) and after 1 hour were dried over anhydrous magnesium sulphate, filtered and evaporated under reduced pressure. The residue was purified by reverse-phase HPLC with gradient 0.1% aqueous ammonium acetate/acetonitrile elution to give the title compound (58 mg) as a foam. MS (APCI) 504 [M+H]+. δ 1HDMSO 0.87 (6H, d), 1.31 (6H, d), 1.99-2.14 (7H, m), 3.19-3.21 (3H, m), 3.45-4.13 (8H, m), 4.40 (1H, sept), 4.56-4.79 (1H, m), 5.48-5.55 (1H, m).
