N2-Acetyl-N6-[(1,1-dimethylethoxy)carbonyl]-L-lysine

White powder

Preparation of ATo a solution of N2-acetyl-N6-(tert-butoxycarbonyl)-L-lysine (576 mg, 2 mmol) and DIPEA (774 mg, 6 mmol) in DMF (8 mL) at 0 C was added HATU (800 mg, 2.1 mmol). After stirring at 0 C for 1 h, (R)-2-phenyl-l-((3aS, 4S, 6S, 7aR)-3a, 5, 5-trimethylhexahydro-4, 6- methanobenzo[d][l, 3, 2]dioxaborol-2-yl)ethan-l-amine (600 mg, 2 mmol) was added. The resulting mixture was stirred at rt for 3 h, before partitioned between HC1 (1 M) and EtOAc. The organic layer was washed with NaHCCb solution, water and brine, before being dried over Na2S04 and filtrated. The filtrate was concentrated to dryness to afford tert-butyl ((S)-5-acetamido-6-oxo-6-(((R)-2-phenyl-l- ((3aS, 4S, 6S, 7aR)-3a, 5, 5- trimethylhexahydro-4, 6-methanobenzo[d][l, 3, 2]dioxaborol-2- yl)ethyl)amino)hexyl)carbamate as an off-white solid (630 mg, 56%).