(E)-(S)-4-((2R,5S)-2-Benzyl-5-tert-butoxycarbonylamino-6-methyl-4-oxo-heptanoylamino)-6-(trityl-carbamoyl)-hex-2-enoic acid ethyl ester

(E)-(S)-4-((2R,5S)-2-Benzyl-5-cyclopentylsulfanylcarbonylamino-6-methyl-4-oxo-heptanoylamino)-6-(trityl-carbamoyl)-hex-2-enoic acid ethyl ester