Preparation of 2-Hydroxymethyl-5,7-dimethyl-3-(2-methylsulfamoyl-phenyl)-4-oxo-3,4-dihydro-quinazoline-6-carboxylic acid ethyl ester: A solution of 2-Benzyloxymethyl-5,7-dimethyl-3-(2-methylsulfamoyl-phenyl)-4-oxo-3,4-dihydro-quinazoline-6-carboxylic acid ethyl ester (15 g, 0.028 mol) in anhydrous THF (270 mL) is degassed under house vacuum. Palladium on activated charcoal (Acros, 10% Pd, 930 mg) is added and the suspension is flushed with hydrogen (balloon). The suspension is stirred under hydrogen overnight. TLC and LCMS analysis indicates that starting material remained. The reaction mixture is filtered through Celite, and the catalyst is washed sequentially with methanol, DCM and methanol. The filtrate is evaporated to give a cream solid. Trituration with diethyl ether provides a white solid which is removed by filtration and dried under high vacuum to provide the title compound (5.42 g, 0.012 mol, 43%). The ethereal filtrate, which contains un-reacted starting material, is evaporated in vacuo and the residue is subjected to a second cycle of hydrogenation (Pd—C, 920 mg): after stirring overnight under hydrogen TLC/LCMS indicated absence of starting material. The reaction mixture is worked-up as above to provide the title compound as a white solid (4.75 g, 0.01 mol, 38%). Total yield: 10.17 g, 0.022 mol, 82%.
