Potent, Novel in Vitro Inhibitors of the <i>Pseudomonas </i><i>a</i><i>eruginosa</i> Deacetylase\nLpxC

Abstract

Deacetylation of uridyldiphospho-3-<i>O</i>-(<i>R</i>-hydroxydecanoyl)-<i>N</i>-acetylglucosamine by LpxC is the\nfirst committed step in the <i>Pseudomonas aeruginosa</i> biosynthetic pathway to lipid A;\nhomologous enzymes are found widely among Gram-negative bacteria. As an essential enzyme\nfor which no inhibitors have yet been reported, the <i>P. aeruginosa </i>LpxC represents a highly\nattractive target for a novel antibacterial drug. We synthesized several focused small-molecule\nlibraries, each composed of a variable aromatic ring, one of four heterocyclic/spacer moieties,\nand a hydroxamic acid and evaluated the LpxC inhibition of these compounds against purified<i>\nP. aeruginosa </i>enzyme. To ensure that the in vitro assay would be as physiologically relevant\nas possible, we synthesized a tritiated form of the specific <i>P. aeruginosa</i> glycolipid substrate\nand measured directly the enzymatically released acetate. Several of our novel compounds,\npredominantly those having fluorinated substituents on the aromatic ring and an oxazoline as\nthe heterocyclic moiety, demonstrated in vitro IC₅₀ values less than 1 μM. We now report the\nsynthesis and in vitro evaluation of these <i>P. </i><i>aeruginosa </i>LpxC inhibitors.