A mixture of 5-isothiocyanato-3-trifluoromethylpyridine-2-carbonitrile (Intermediate 10, 582 mg, 2.54 mmol) and 4-(4-(1-cyanocyclobutylamino)phenyl)butanoic acid (Intermediate 80, 410 mg, 1.59 mmol) in DMF (3 mL) was stirred at room temperature overnight. To this mixture were added methanol (4 mL) and HCl (2M, 2 mL) and the resulting mixture was refluxed for 3 h. After being cooled room temperature, the reaction mixture was poured into cold water and extracted with EtOAc (3×). The organic layers were dried over magnesium sulfate and concentrated to dryness. Column chromatography of the residue on silica gel (Hexane:EtOAc=4:1) afforded 256 mg of methyl 4-(4-(7-(6-cyano-5-(trifluoromethyl)-pyridin-3-yl)-8-oxo-6-thioxo-5,7-diazaspiro[3.4]octan-5-yl)phenyl)butanoate as a white solid. 1H NMR (400 MHz, CDCl3) δ 9.11 (d, 1H), 8.38 (d, 1H), 7.42 (d, 2H), 7.36-7.19 (m, 2H), 3.70 (s, 3H), 2.87-2.75 (m, 2H), 2.75-2.53 (m, 4H), 2.42 (t, 2H), 2.26 (m, 1H), 2.05 (m, 2H), 1.78-1.61 (m, 1H). LCMS [M+1]+ 503.0.
