Sodium metal (4.4 g, 19 mmol) was added to benzyl alcohol (100 ml) at ambient temperature and the mixture stirred for 30 minutes then heated at 80° C. for 1 hour. The mixture was then cooled to 40° C. and 7-fluoro-3,4-dihydroquinazolin-4-one (7.8 g, 47 mmol) was added. The reaction mixture was stirred at 130° C. for 4 hours and allowed to cool to ambient temperature and stirred for 18 hours. The solution was quenched with water (800 ml) and acidified to pH3 with concentrated hydrochloric acid. The resulting precipitate was collected by filtration, washed with water and ether and dried for 4 hours at 60° C. under high vacuum to give 7-benzyloxy-3,4-dihydroquinazolin-4-one (7.02 g, 63%). 7-Benzyloxy-3,4-dihydroquinazolin-4-one (7.0 g, 27 mmol) was suspended in dry DMF (50 ml) and sodium hydride was added (1.22 g of a 60% suspension in mineral oil, 30 mmol). The reaction mixture was allowed to return to ambient temperarture, chloromethyl pivalate (4.75 g, 31.5 mmol) was added over 10 minutes and the mixture was stirred for 1 hour. The reaction mixture was quenched into water (250 ml), the aqueous phase adjusted to pH5 with 2M hydrochloric acid and extracted with ether (3×300 ml). The combined ether phases were washed with brine, dried (MgSO4) and the volatiles were removed by evaporation. The solid residue was triturated with isohexane, collected by filtration and dried under vacuum to give 7-benzyloxy-3-((pivaloyloxy)methyl)-3,4-dihydroquinazolin-4-one (9.1 g, 90%). 7-Benzyloxy-3-((pivaloyloxy)methyl)-3,4-dihydroquinazolin-4-one (8.0 g, 22 mmol) was dissolved in TFA (40 ml) and the mixture was heated at reflux for 3 hours then allowed to cool to ambient temperature and stirred for 18 hours. The TFA was removed by evaporation and the residue resuspended in a mixture of ether and aqueous sodium hydrogen carbonate solution. The solid was collected by filtration, washed with water and ether and dried at 40° C. for 3 hours under high vacuum to give 7-hydroxy-3-((pivaloyloxy)methyl)-3,4-dihydroquinazolin-4-one (5.42 g, 90%).
