title: Synthesis and evaluation of 3-(dihydroxyboryl)benzoic acids as D,D-carboxypeptidase R39 inhibitors.
abstract: Penicillin binding proteins (PBPs) catalyze steps in the biosynthesis of bacterial cell walls and are the targets for the beta-lactam antibiotics. Non-beta-lactam based antibiotics that target PBPs are of interest because bacteria have evolved resistance to the beta-lactam antibiotics. Boronic acids have been developed as inhibitors of the mechanistically related serine beta-lactamases and serine proteases; however, they have not been explored extensively as PBP inhibitors. Here we report aromatic boronic acid inhibitors of the D,D-carboxypeptidase R39 from Actinomadura sp. strain. Analogues of an initially identified inhibitor [3-(dihydroxyboryl)benzoic acid 1, IC(50) 400 microM] were prepared via routes involving pinacol boronate esters, which were deprotected via a two-stage procedure involving intermediate trifluorborate salts that were hydrolyzed to provide the free boronic acids. 3-(Dihydroxyboryl)benzoic acid analogues containing an amide substituent in the meta, but not ortho position were up to 17-fold more potent inhibitors of the R39 PBP and displayed some activity against other PBPs. These compounds may be useful for the development of even more potent boronic acid based PBP inhibitors with a broad spectrum of antibacterial activity.
authors.affiliation: Department of Chemistry, University of Oxford, Oxford, UK.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Inglis
authors.forename: Astrid
authors.initials: A
authors.lastname: Zervosen
authors.forename: Esther C Y
authors.initials: EC
authors.lastname: Woon
authors.forename: Thomas
authors.initials: T
authors.lastname: Gerards
authors.forename: Nathalie
authors.initials: N
authors.lastname: Teller
authors.forename: Delphine S
authors.initials: DS
authors.lastname: Fischer
authors.forename: André
authors.initials: A
authors.lastname: Luxen
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Schofield
mesh_terms: D000192:Actinomycetales / Q000201:enzymology; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors; D019817:Benzoic Acid / Q000138:chemical synthesis / Q000494:pharmacology*; D001897:Boronic Acids; D002268:Carboxypeptidases / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001897:Boronic Acids; D004791:Enzyme Inhibitors; D019817:Benzoic Acid; D002268:Carboxypeptidases