The general procedure for the synthesis of Cbz-arginine from cyanamide and (S)-5-amino-2-(benzyloxycarbonyloxyamino)pentanoic acid was as follows: to a solution of water (2.5 mL) containing p-methoxyaniline (1b, 61.6 mg, 0.50 μmol) and cyanamide (25.2 mg, 0.60 μmol) was added scandium trifluoromethanesulfonate (Sc(OTf)3, at room temperature. 24.6 mg, 50 nmol). The reaction mixture was stirred at 100 °C for 2 days. After completion of the reaction, the reaction mixture was washed with chloroform (3 x 10 mL) extraction. The aqueous layer was separated and concentrated under vacuum. The residue was purified by filtration through a silica gel pad (eluent: chloroform-methanol, 20:1, v/v).
