24424-99-5

294-90-6

175854-39-4

A solution of chloroform (10 mL) of di-tert-butyl dicarbonate (1.77 g, 8.12 mmol) was slowly added dropwise through a constant pressure dropping funnel to a solution of chloroform (40 mL) containing rotundin (0.51 g, 2.90 mmol) and triethylamine (1.25 mL, 8.99 mmol). The reaction mixture was stirred at room temperature overnight and then concentrated by rotary evaporator. The resulting crude product was purified by silica gel column chromatography using gradient elution from ethyl acetate to 5% methanol/dichloromethane to afford the target compound 1,4,7-tri-tert-butoxycarbonyl-1,4,7,10-tetraazacyclododecane as a white solid (1.02 g, 80% yield). The product characterization data were in agreement with literature reports.