(1S,2S)-1,2-Cyclopropanedicarboxylic Acid 1,2-Diethyl Ester is an intermediate in synthesizing (O846925), (2S,3S)-2,3-Oxiranedicarboxylic Acid Monoethyl Ester is used in the synthesis of aza-peptidyl inhibitors of lysosomal asparaginyl endopeptidase, legumain. Also used in the synthesis of irreversible epidermal growth factor receptor inhibitors and probes for cathespins.