187223-15-0

187223-14-9

187223-15-0

Step III: Preparation of Fmoc-(2S,4R)-(4-O-CO-NH-CH2-CH2-NH-Boc)-Pro-OH. the methyl ester obtained in step II was converted to free acid by hydrolysis reaction. This is done by adding 1N sodium hydroxide solution to a mixed solvent of 1,4-dioxane and water for the reaction. This step produced a mixture of H-(2S,4R)-(4-O-CO-NH-CH2-CH2-NH-Boc)-Pro-OH with the target product Fmoc-(2S,4R)-(4-O-CO-NH-CH2-CH2-NH-Boc)-Pro-OH. The reaction yield was 55%.