Disclosed herein are hydroxamic acid derivatives of formula [1], wherein the substituents are as defined within the specification, processes for preparing them, composition comprising said compounds and uses thereof. Said compounds are useful as inhibitors of uridyldiphospho(UDP)-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) and as antimicrobial. Particularly preferred compounds include: 2-[{ [4-(fluoromethyl)biphenyl-4-yl]carbonyl} (methyl)amino]-N-hydroxy-N-methylpropanediamide, 2-{ [4-(2,3-dihydro-1-benzofuran-6-yl)benzoyl](methyl)amino} -N-hydroxy-N-methylpropanediamide N-(cyclopropylmethyl)-N-hydroxy-2-({ [4-(2-hydroxyethoxy)biphenyl-4-yl]carbonyI} amino)propanediamide, N-hydroxy-2-({ [4-(2-hydroxyethoxy)biphenyl-4-yl]carbonyl} amino)-N-[2-(propan -2-yloxy)ethyl]propanediamide, N-hydroxy-2-({ [4-(2-hydroxyethoxy)biphenyl-4-yl]carbonyl} amino)-N-(1,3-thiazol-5-ylmethyl)propanediamide, N-(furan-2-ylmethyl)-N-hydroxy-2-({ [4-(2-hydroxyethoxy)biphenyl-4-yl]carbonyI} amino)propanediamide.
