DIPEA (0.036 mL, 0.21 mmol) was added to a cold (0° C.) mixture of (4S,7S,10aS)-4-(tert-butoxycarbonylamino)-5-oxooctahydro-2H-pyrido[2,1-b][1,3]thiazepine-7-carboxylic acid (55 mg, 0.16 mmol), thiazol-2-amine (19.2 mg, 0.192 mmol) and 1-hydroxy-7-azabenzotriazole (26.1 mg, 0.192 mmol) in DMF (0.6 mL). Then EDC (36.7 mg, 0.192 mmol) was added. The reaction was stirred at rt for 8 hr. The crude mixture was purified by RP prep-HPLC (Method B) to give tert-butyl (4S,7S,10aS)-5-oxo-7-(thiazol-2-ylcarbamoyl)octahydro-2H-pyrido[2,1-b][1,3]thiazepin-4-ylcarbamate (35 mg, 0.082 mmol, 51% yield) as a white solid. Anal. Calcd. for C18H26N4O4S2 m/z 426.5. found: 427.1 (M+H)+; 1H NMR (400 MHz, CDCl3) δ ppm 7.45 (s, 1H), 6.98 (s, 1H), 5.96 (m, 1H), 5.37 (br s, 1H), 5.28 (br s, 1H), 3.35 (m, 2H), 2.94 (m, 2H), 2.36 (m, 1H), 2.45 (m, 1H), 2.05 (m, 2H), 1.53-1.50 (m, 4H), 1.50 (s, 9H).
