The development of iminocyclitol-based small molecule libraries against a bacterial TGase is described. An iminocyclitol was conjugated with a pyrophosphate mimic using either a 1,3-dipolar cycloaddition or reductive amination reaction, which was then condensed with a variety of lipophilic carboxylic acids in an amide bond coupling to generate a desired molecular library. With assistance of microtiter plate-based combinatorial chemistry and in situ screening, a potential inhibitor, the first potent iminocyclitol-based inhibitor against bacterial TGases was efficiently developed.