N-Acyl-3-amino-5H-furanone derivatives as new inhibitors of LuxR-dependent quorum sensing: Synthesis, biological evaluation and binding mode study Jane Estephane a,b , Julien Dauvergne a,b , Laurent Soulère a,b, * , Sylvie Reverchon c , Yves Queneau a,b , Alain Doutheau a,b, * a INSA Lyon, Institut de Chimie et Biochimie Moléculaires et Supramoléculaires, Laboratoire de Chimie Organique, Bât J. Verne, 20 av A. Einstein, 69621 Villeurbanne Cedex, France b CNRS, UMR 5246 ICBMS, Université Lyon 1, INSA-Lyon, CPE-Lyon, Bât CPE, 43 bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France c Unité Microbiologie, Adaptation et Pathogénie, UMR CNRS-UCBL-INSA-BAYER CROPSCIENCE 5240, Université Lyon 1, INSA-Lyon, Domaine Scientifique de la Doua, Villeurbanne, France article info Article history: Received 14 May 2008 Revised 25 June 2008 Accepted 25 June 2008 Available online 28 June 2008 Keywords: Quorum sensing AHLs LuxR Antagonist V. fischeri Molecular modelling Docking abstract New N-acyl homoserine lactone analogues, N-acyl-3-amino-5H-furanone derivatives and some 4-halo- geno counterparts, were synthesised and tested for their ability to modulate LuxR-dependent bacterial quorum sensing. Both types of analogues proved to be inhibitors, the halogenated compounds being sig- nificantly more active. Molecular modelling suggested that the conjugated enamide group induces two preferential conformations leading to specific binding modes. In addition, the presence of the halogen atom could enhance the fitting of the lactone ring through specific interactions with strictly conserved or conservatively replaceable residues in the LuxR protein family, namely Asp79, Trp94 and Ile81. Ó 2008 Elsevier Ltd. All rights reserved. Bacteria are able to communicate through small diffusible mol- ecules called autoinducers. The concentration of these chemical messengers in a specific environment reflects the bacterial density and, when a critical concentration is reached, bacteria change their biological activities. This cell to cell communication system, named ‘quorum sensing’, allows bacteria to coordinate their behaviour for a specific activity, such as biofilm formation or virulence, 1–4 ren- dering it an attractive target for the conception of new antibacte- rial agents. 5–12 In Gram-negative bacteria, the quorum sensing is orchestrated by N-acyl-L-homoserine lactones (AHLs) acting as autoinducers, AHL synthase, an AHL-dependent transcriptional regulator and specific genes encoding different phenotypes. 13 Pre- viously we have reported the antagonist activity and molecular modelling studies of AHL analogues with structural modifications on the acyl moiety, either with a terminal aromatic group 14 or resulting from the replacement of the amide function by sulfon- amide or urea functions. 15–18 We present here the synthesis, the biological evaluation and the binding mode study of new AHL ana- logues, namely 3-amino-5H-furanone derivatives 5–7 and some 4- halogenated counterparts 8–10 (Scheme 1). Compounds 5–7 were designed to evaluate the modulation of the antagonist activity in- duced by conformational and H-bonding modifications resulting from the replacement of the amide by an enamide function. Be- cause of their analogy with natural brominated furanones, known to be quorum sensing inhibitors which display antimicrobial activ- ities, 19–21 the halogenated analogues 8–10 were also prepared. The 3-amino-5H-furanone derivatives 5–10 were obtained from known 22 3-amino-5H-furan-2-one (2) prepared by reacting so- dium azide with a-bromo-c-butyrolactone (1) in dimethylform- amide (Scheme 1). 23 This compound 2 was further halogenated with N-bromo or N-chloro-succinimide to afford known 24 3-ami- no-4-bromo-5H-furan-2-one (3) and 3-amino-4-chloro-5H-furan- 2-one (4), respectively. The furanones 2–4 were then acylated with acyl chlorides under standard conditions to furnish the compounds 5 and 7–10. Compound 6 was prepared by acylation of Meldrum’s acid with butyryl chloride and then by further reaction with 2. Pure 6 was obtained in low yield because crude product was a mixture of 6 and of N-butanoyl-3-amino-5H-furan-2-one, arising from reaction between 2 and butyryl chloride, two compounds that proved to be difficult to separate by column chromatography. 0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmcl.2008.06.090 * Corresponding authors. Fax: +33 472 43 88 96 (A.D.). E-mail addresses: laurent.soulere@insa-lyon.fr (L. Soulère), alain.doutheau@insa- lyon.fr (A. Doutheau). Bioorganic & Medicinal Chemistry Letters 18 (2008) 4321–4324 Contents lists available at ScienceDirect Bioorganic & Medicinal Chemistry Letters journal homepage: www.elsevier.com/locate/bmcl