(4S,5S)-4-Isobutyl-2,2-dimethyl-5-{(1R,2R)-4-oxo-2-[(S)-1-(2,2,2-trichloro-ethoxycarbonyl)-ethylcarbamoyl]-cyclopentyl}-oxazolidine-3-carboxylic acid tert-butyl ester

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

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

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

(S)-2-({(1R,2R)-2-[(1S,2S)-2-((S)-2-tert-Butoxycarbonylamino-4-methylsulfanyl-butyrylamino)-1-hydroxy-4-methyl-pentyl]-4-oxo-cyclopentanecarbonyl}-amino)-propionic acid 2,2,2-trichloro-ethyl ester