To a solution of 8-bromo-7-(4-chlorobenzyl)-3-methyl-1H-purine-2,6(3H,7H)-dione (100 mg, 0.27 mmol, intermediate 8) in DMF (5 mL) was added propane-1-thiol (24.7 mg, 0.32 mmol) followed by potassium carbonate (112.2 mg, 0.81 mmol). The reaction was stirred at 60° C. for 4 h. The reaction was cooled and partitioned between ethyl acetate and water. The organic phase was washed with brine, dried over sodium sulfate, filtered and concentrated to give a crude white solid product (124 mg, 99.9% yield). LCMS MH+ 365.
