sodium hydroxide in 1,4-dioxane; water pH 9.5;

1: 76 percent / NaOH / methanol / 6 h / Heating 2: dicyclohexylcarbodiimide (DCC) / ethyl acetate; dimethylformamide / 1.) -5 deg C, overnight, 2.) RT, 4 h 3: 71 percent / anisole, TFA / CH2Cl2 View Scheme

1: H-tyrosine(t-Bu)-OH With N,N-dicyclohexylamine in acetone T=20°C; 2: 1-[[(9H-fluoren-9-ylmethoxy)carbonyl]oxy]-2,5-pyrrolidinedione With sodium carbonate in water; acetonitrile T=0 - 20°C; pH=8; 3: With potassium hydrogensulfate in water; acetonitrile pH=2 - 3;