N-Cbz-(2S)-4,4-difluoroglutamic acid α-tert-butyl ester γ-glutamic acid α-tert-butyl γ-2-(trimethylsilyl)ethyl ester

N-Boc-Abz-4,4-difluoroglutamic acid α-tert-butyl ester γ-glutamic acid α-tert-butyl γ-2-(trimethylsilyl)ethyl ester