“…Boc-Arg-OH-HCl (16). Arginine hydrochloride (21.05 g, 0.1 mol) was dissolved in a mixture of dioxane (200 mL) and 0.5 N NaOH (200 mL), the solution was cooled to 0 °C (i-BuO)2CO (24 g, 0.14 mol), and 4 N NaOH (12.5 mL, 0.05 mol) was added with vigorous stirring, which was continued for 2 h. Some insoluble material was removed by filtration, and the filtrate was extracted with Et^O (2 X 100 mL). The aqueous phase was cooled to 0 °C, acidified (pH 5) with 1 N HC1, extracted with CHC13 (3 X 100 mL), neutralized (pH 7.3) with 1 N NaOH, and evaporated.…”