To a solution of 4.0 g of 5-[1,1'-biphenyl]-4-yl-9-fluoro-3-methyl-1H-[1,3]oxazino[4,5-c] quinoline-1-one in 200 ml of tetrahydrofuran at 0° C. was added 0.91 g of sodium borohydride. The solution was stirred at 0° C. for 1 hour, then allowed to warm to 20° C. and stirred for 12 hours. A 50 ml portion of water was added and the foaming solution stirred for 10 minutes. The volatiles were removed in vacuo, then 40 ml of 0.5N sodium hydroxide was added and the solution extracted with two 100 ml portions of dichloromethane. The extracts were combined, extracted with 100 ml of water containing 5 ml of 1N sodium hydroxide and the aqueous layer from this extraction extracted with 100 ml of dichloromethane. The aqueous layers were combined, filtered through celite and acidified to pH 4 with 3 % aqueous hydrochloric acid. The resulting solid was collected, washed with water and dried, giving 2.8 g of the desired product as a yellow solid, mp 180°-182° C. (dec.)
