(2S,4S)-4-allyl-5-oxopyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-methyl ester

(2S,4R)-4-allyl-5-oxopyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester 2-methyl ester

dimethyl (2S)-2-{(tert-butoxy)-N-[(tert-butyl)oxycarbonyl]carbonylamino}heptanedioate

(E)-(S)-4-{(2R,4S,5S)-4-Hydroxy-6-methyl-2-(3-methyl-but-2-enyl)-5-[(5-methyl-isoxazole-3-carbonyl)-amino]-heptanoylamino}-5-((S)-2-oxo-pyrrolidin-3-yl)-pent-2-enoic acid ethyl ester

(E)-(S)-4-[(2R,4S,5S)-2-Benzyl-5-tert-butoxycarbonylamino-4-(tert-butyl-dimethyl-silanyloxy)-6-methyl-heptanoylamino]-5-((S)-2-oxo-pyrrolidin-3-yl)-pent-2-enoic acid ethyl ester