Aziridine analogues of diaminopimelic acid (DAP) have been prepared stereoselectively for the first time and evaluated as inhibitors of DAP epimerase. (2R,3S,3′S)-3-(3′-Aminopropane)aziridine-2,3′-dicarboxylate 4 was synthesised and shown to be a reversible inhibitor of DAP epimerase with an IC₅₀ value of 2.88 mM. (2S,4S)- and (2S,4R)-2-(4-Amino-4-carboxybutyl)aziridine-2-carboxylic acid (LL-azi-DAP 14 and DL-azi-DAP 29) were made as pure diastereomers, and both were shown to be irreversible inhibitors of DAP epimerase. LL-Azi-DAP 14 selectively binds to Cys-73 of the enzyme active site whereas DL-azi-DAP 29 binds to Cys-217 via attack of sulfhydryl on the methylene of the inhibitor aziridine ring. These observations are consistent with the two base mechanism proposed for the epimerisation of LL-DAP 1 and meso-DAP 2 by DAP epimerase.