[(S)-1-((S)-1-{(S)-[(1R,2R)-2-((S)-1-Butylcarbamoyl-2-methyl-propylcarbamoyl)-4-oxo-cyclopentyl]-hydroxy-methyl}-3-methyl-butylcarbamoyl)-3-methylsulfanyl-propyl]-carbamic acid tert-butyl ester

(4S)-isobutyl-(5S)-((2R)-methoxycarbonyl-cyclopentyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid tert-butyl ester

(5S)-((2R)-butylcarbamoyl-cyclopentyl)-(4S)-isobutyl-2,2-dimethyloxazolidine-3-carboxylic acid tert-butyl ester

(4S,5S)-5-[(1R,2R)-2-((S)-1-Benzyloxycarbonyl-2-methyl-propylcarbamoyl)-cyclopentyl]-4-isobutyl-2,2-dimethyl-oxazolidine-3-carboxylic acid tert-butyl ester

(4S,5S)-5-[(1R,2R)-2-((S)-1-Butylcarbamoyl-2-methyl-propylcarbamoyl)-4-oxo-cyclopentyl]-4-isobutyl-2,2-dimethyl-oxazolidine-3-carboxylic acid tert-butyl ester