(4R,5S)-4-benzyloxycarbonylamino-5-methyl-3-oxo-heptanoic acid methyl ester

({(2S,3R,4S,5S)-3-[(1S,2S)-1-(3,5-Difluoro-benzyloxy)-2-methyl-butyl]-4-nitro-5-phenyl-pyrrolidine-2-carbonyl}-amino)-acetic acid methyl ester

({(2S,3R,4S,5S)-3-[(1S,2S)-1-(2,3-Difluoro-benzyloxy)-2-methyl-butyl]-4-nitro-5-phenyl-pyrrolidine-2-carbonyl}-amino)-acetic acid methyl ester

{[(2S,3R,4S,5S)-3-((1S,2S)-1-Benzyloxy-2-methyl-butyl)-5-cyclopropyl-4-nitro-pyrrolidine-2-carbonyl]-amino}-acetic acid methyl ester

(2S,3R,4S,5S)-3-[(1S,2S)-1-(benzyloxy)-2-methylbutyl]-5-cyclopropyl-4-nitropyrrolidine-2-carboxylic acid