Methanesulfonyl chloride → [6-(4,4-Dimethylcyclohexyl)-2-methylthieno[2,3-d]pyrimidin-4-yl]methyl methanesulfonate

To a mixture of [6-(4,4-dimethylcyclohexyl)-2-methylthieno[2,3-d]pyrimidin-4-yl]methanol (16.0 g), TEA (10 mL) and DCM (200 mL) was added dropwise MsCl (5.0 mL) at 0° C. for 15 minutes, followed by stirring at the same temperature for 1 hour. To the reaction mixture was added saturated aqueous sodium bicarbonate, followed by extraction with chloroform. The organic layer was washed sequentially with saturated aqueous sodium bicarbonate and brine. To the organic layer were added MgSO4, activated carbon (5 g), and basic silica gel (20 mL), followed by stirring. The mixture was filtered through Celite and then concentrated under reduced pressure to obtain [6-(4,4-dimethylcyclohexyl)-2-methylthieno[2,3-d]pyrimidin-4-yl]methyl methanesulfonate (18.9 g).