Pathogenicity of Yersinia pestis (Y. pestis) relies on several effector proteins, including YopH, a protein-tyrosine phosphatase. Previously, we screened a library of analogues based on the ubiquitous PTP substrate, p-nitrophenylphosphate (pNPP) and found that incorporation of a 3-phenyl substituent (6-nitro-[1,1'-biphenyl]-3-yl dihydrogen phosphate (1)) enhanced affinity. The current study reports the conversion of 1 from a substrate to inhibitor by replacing the hydrolysable phosphoryl group with a 3-isoxazolecarboxylic acid moiety and by introduction of an aminooxy group and subsequent diversification using oxime-based click chemistry. As reported herein, this approach led to the identification of non-promiscuous low micromolar affinity bidentate YopH inhibitors.