(S)-1-[(S)-4-Methyl-2-((S)-3-methyl-2-{(S)-3-phenyl-2-[((S)-pyrrolidine-2-carbonyl)-amino]-propionylamino}-butyrylamino)-pentanoyl]-pyrrolidine-2-carboxylic acid tert-butyl ester

leucylproline tert-butyl ester

(S)-1-[(S)-2-((S)-2-Amino-3-methyl-butyrylamino)-4-methyl-pentanoyl]-pyrrolidine-2-carboxylic acid tert-butyl ester

Fluorenylmethoxycarbonylleucyl-proline tert-butyl ester

(S)-1-{(S)-2-[(S)-2-((S)-2-Amino-3-phenyl-propionylamino)-3-methyl-butyrylamino]-4-methyl-pentanoyl}-pyrrolidine-2-carboxylic acid tert-butyl ester