The invention is to provide a novel compound that is useful as a medical drug in that said compound displays strong antimicrobial activity against gram-negative bacteria such as Pseudomonas aeruginosa and drug-resistant strains thereof, on the basis of LpxC-inhibiting activity. The novel compound is a hydroxamic acid derivative represented by general formula 1 (1) or a pharmaceutically acceptable salt thereof.本發明之課題在於提供一種基於LpxC阻礙作用而對綠膿桿菌等之革蘭氏陰性細菌及其抗藥性菌顯示出強抗菌活性,且可用作為醫藥品之新穎之化合物。上述課題之解決方法乃是提供以下述一般式所示之異羥肟酸衍生物或其藥學上所容許之鹽
