To a suspension of 2.1 g of lithium aluminum hydride in 200 ml of tetrahydrofuran was added 6.06 g of trans-4a,5,6,11b-tetrahydro-4-isopropyl-10-fluoro-2H-[1]benzoxepino[5,4-b]-1,4-oxazin-3(4H)-one in portions and the mixture was then refluxed for about one hour. The mixture was then cooled in ice, decomposed by the addition of 6 ml of 10% aqueous sodium hydroxide solution, and stirred for 16 hours. The solids present in the reaction mixture were separated by filtration and washed with water and the solvent was evaporated from the filtrate to leave a residual oil. The oil was dissolved in ether and a solution of methanesulfonic acid in ether was added until no more cloudiness occurred on addition. The solid was then separated by filtration and triturated in ether to give a tacky solid. This solid was recrystallized from a mixture of methanol and ethyl acetate to give trans-10-fluoro-4-isopropyl-3,4,4a,5,6,11b-hexahydro-2H-[1]benzoxepino[5,4-b]-1,4-oxazine methanesulfonate melting at about 163°-165° C.
