(S)-1-tert-Butyl 2-methyl 4,4-difluoropyrrolidine-1,2-dicarboxylate1-tert-Butyl 2-methyl (2S)-4,4-difluoro-1,2-pyrrolidinedicarboxylateN-Boc-4,4-二氟-L-脯氨酸甲酯tert-Butyl (2S)-2-(methoxycarbonyl)-4,4-difluoropyrrolidine-1-carboxylate1-叔丁基-2-甲基-(2S)-4,4-二氟吡咯烷-1,2-二羧酸酯(2S)-2-(甲氧羰基)-4,4-二氟吡咯烷-1-羧酸叔丁酯N-Boc-4,4-Difluoro-L-proline methyl ester