Triethylamine → Boc-Lys(Z)-OtBu N-Phenylmethoxycarbonyl

tert-Butyl 2-amino-6-benzyloxycarbonylamino-hexanoate (1.0 g, 2.68 mmol) was dissolved in N,N-dimethylformamide (50 mL) and then triethylamine (5.35 mmol, 0.75 mL) followed by N-(tert-butoxycarbonyloxy)succinimide (0.72 g, 3.35 mmol) was added to the solution. The mixture was stirred overnight and then concentrated. The product was purified from the residue by silica gel chromatography (20% MeOH/chloroform) to give tert-butyl 6-benzyloxycarbonylamino-2-tert-butoxycarbonylamino-hexanoate. The tri-protected product was reduced on a Parr hydrogenator (50 psi) to remove the benzyloxycarbonyl protecting group. The solvents were removed to give tert-butyl 6-amino-2-tert-butoxycarbonylamino-hexanoate (0.65 g, 80%).