The solution of 7.5 g of the slow moving 1-(2-isopropylaminopropyl)-9-methoxy-3,4,5,5a,6,7-hexahydro-2H-naphth[1,2-d]azepin-2-one (Example 1) in 125 ml of methylene chloride is added slowly to 125 ml of a stirred 10 percent solution of boron tribromide in methylene chloride, precooled in a dry ice-acetone bath. The mixture is allowed to warm to room temperature slowly and is stirred overnight. It is cooled in an ice bath, 100 ml of water and 100 ml of 3 N aqueous sodium hydroxide are added and stirring is continued for one half hour. The basic aqueous solution is separated, washed with diethyl ether, neutralized to pH=8-9 with hydrochloric acid and allowed to stand overnight. The product, collected by filtration and subsequent extraction with chloroform, is suspended in 5 percent aqueous sodium bicarbonate and the suspension is stirred for 4 hours. The insoluble product is collected, dried and recrystallized from ethanol, to yield 1-(2-isopropylaminopropyl)-9-hydroxy-3,4,5,5a,6,7-hexahydro- 2H-naphth[1,2-d]azepin-2-one as a single diastereoisomer, melting at 202°-204°.
