(2S,3S)-1-(benzyloxycarbonyl)-3-n-butyl-glutamic acid

(2S,3S)-2-(4-methyl-2,6,7-trioxa-bicyclo[2.2.2]oct-1-yl)-5-oxo-3-(4-chlorophenyl)-pyrrolidine-1-carboxylic acid benzyl ester