The stereoselective synthesis of aziridine analogues of diaminopimelic acid (DAP) and their interaction with dap epimerase

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 IC ₅₀ 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.