31972-52-8

556-50-3

24424-99-5

31972-52-8

GENERAL METHODS: Amino acids or peptides (1 mmol) were added dropwise to a solution of ethanol (1 mL) containing guanidine hydrochloride (15 mmol) and di-tert-butyl dicarbonate (2.5-3 mmol) under stirring conditions, and the temperature of the reaction was maintained at 35-40°C. The reaction mixture was stirred continuously until a clarified solution was formed. Subsequently, the ethanol was removed by evaporation under reduced pressure. The residue was washed sequentially with distilled water (2 mL) and hexane or petroleum ether (2 mL) to obtain high purity N-Boc amino acids or N-Boc peptides. If further improvement of product purity is required, the crude product can be purified by recrystallization.