Herein we report a scaffold-hopping approach to identify a new scaffold with a zinc binding headgroup. Structural information was used to give novel oxazolidinone-based LpxC inhibitors. In particular, the most potent compound, 23j, showed a low efflux ratio, nanomolar potencies against E. coli LpxC enzyme, and excellent antibacterial activity against E. coli and K. pneumoniae. Computational docking was used to predict the interaction between 23j and E. coli LpxC, suggesting that the interactions with C207 and C63 contribute to the strong activity. These results provide new insights into the design of next-generation LpxC inhibitors.KEYWORDS: Antibacterial, Gram-negative bacteria, LpxC, scaffold hopping, oxazolidinone I n recent years, infections caused by antibiotic-resistant bacteria have emerged as major threats to human communities worldwide. 1 However, the late-stage clinical development pipeline for antibacterials has been unacceptably lean in recent decades. 2 In particular, no drugs have reached advanced stages of development for the treatment of infection due to multidrug-resistant Gram-negative bacteria. Thus, there is a great need to develop new mechanisms by which Gramnegative antibacterial agents can combat bacterial antibiotic resistance. 3,4 One of the emerging targets in Gram-negative bacteria is LpxC, an essential enzyme in the lipid A biosynthetic pathway. Because LpxC does not show homology to any mammalian protein, it is a promising antibiotic target for developing novel therapeutics against multidrug-resistant Gram-negative pathogens. 5 LpxC inhibitors have drawn much attention in new entities for Gram-negative antibacterial agents. 6 To date, extensive investigations have been carried out on the mechanism underlying the LpxC enzyme. 7,8 Those studies have identified a zinc ion to catalyze deacetylation and a hydrophobic tunnel binding a myristate fatty acyl chain of the natural substrate. Merck researchers discovered 1 (L-161,240) containing an oxazoline scaffold in the mid-1990s, 6 and recently several LpxC inhibitors have been reported as antibacterial agents, 9−17 although to our knowledge none have reached the market yet.Among the well-characterized compounds, threonyl-hydroxamate derivatives are representative LpxC inhibitors, such as 2 (CHIR-090) and 3 (LPC-009) (Figure 1a). 18,19 According to a few reports on the binding modes of these compounds, the threonyl-hydroxamate group of 2 and that of 3 occupy the active site, and its diphenyl acetylene or phenyl-diyne group penetrates the hydrophobic passage. 19−21 Herein we report a scaffold hopping approach to identify a new scaffold with a zinc-binding headgroup. Additionally, we describe the synthesis, biological evaluation, and docking analysis of oxazolidinone-based LpxC inhibitors. Among these compounds, 23j showed remarkable antibacterial activity.