(S)-tert-butyl 4-(1-cyano-2-(3′-cyanobiphenyl-4-yl)ethylcarbamoyl)tetrahydro-2H-pyran-4-ylcarbamate (Example 8, step (ii), 282 mg) in formic acid (1.5 mL) was stirred at room temperature for 5 h, warmed at 36° C. for 30 mins then stirred at room temperature overnight. Water was added and the cooled solution was made basic with 0.880 ammonia and then extracted (×3) with dichloromethane. The combined organic extracts were dried over magnesium sulphate, filtered and the solvent was evaporated to yield an oil which was purified by chromatography on silica using 80% ethyl acetate in isohexane as eluent and then crystallised from isopropanol to yield a solid. The solid was washed with diethyl ether and dried to afford the titled compound (89 mg).
