Transfer ribonucleic acid (tRNA) synthetase inhibitors, salts, and pharmaceutically acceptable compositions thereof of the general formula: wherein Ar is aryl and heteroaryl; L is —C(O)N(Q)CH2—, or —CR10R11OCR12R13—; Q is hydrido, —(CH2)mCO2H and —(CH2)mCO2CH3, m is 1, 2, 3, and 4; R1, R2, R9, R10, R11, R12 and R13 are hydrido or lower alkyl; wherein Het is a heterocyclic moiety, the inhibitors are suitable for use as antimicrobial agents.