Click Chemistry DOI: 10.1002/ange.200800862 Construction and Screening of a 2-Aminoimidazole Library Identifies a Small Molecule Capable of Inhibiting and Dispersing Bacterial Biofilms across Order, Class, and Phylum** Steven A. Rogers and Christian Melander* Bacterial biofilms are defined as a surface-attached commun- ity of bacteria that are surrounded by a protective extra- cellular matrix. [1] Within the biofilm state, bacteria display differential gene expression and are at least 1000-fold more resistant to antibiotic treatment. [2] Biofilms account for more than 80% of all bacterial infections; they drive persistent infection of indwelling medical devices, and are responsible for the mortality and morbidity of almost all cystic fibrosis (CF) patients. [3–6] Given the biomedical prominence of biofilms, there have been significant efforts to discover small molecules that modulate biofilm development. [1] We have shown that simple derivatives of the marine natural product bromoageliferin will both inhibit and disperse bacterial biofilms (Scheme 1). [7–11] Recently, we demonstrated that dihydrosventrin (DHS) inhibits and disperses Pseudomonas aeruginosa (multiple strains), Acinetobacter baumannii, and Bordetella bronchi- septica biofilms, [7] making it the first small molecule reported to inhibit and disperse biofilms across bacterial order and class through a nonbactericidal mechanism. We have begun to investigate whether modifications to the core DHS structure will lead to derivatives with enhanced anti-biofilm activities. [8] One of the first structural variations we have studied is replacement of the pyrrole subunit with a triazole subunit (Scheme 2). Herein we detail the develop- ment of the synthetic protocols necessary to access 2-amino- imidazole/triazole conjugates (2-AITs), the application of these methods to the synthesis of a focused 2-AIT library, and the discovery of small molecules that inhibit and disperse bacterial biofilms across order, class, and phylum. Given that there is a paucity of reactions that have been reported to be compatible with 2-aminoimidazoles, we deemed the Cu I -catalyzed [3+2] alkyne/azide cycloaddition (click reaction) [12–14] as a promising method to generate 2- AITs given the broad substrate range displayed by this reaction. To test the applicability of the reaction, we synthesized the alkynyl-substituted 2-aminoimidazole (2-AI, 1) and tested its ability to participate in a Cu I -catalyzed [3+2] cycloaddition with benzyl azide. Amino acid 2 [15] was subjected to a small-scale Akabori reduction, [16] which, followed by condensation with cyan- amide [17] delivered the target alkyne 1 in 88% yield (Scheme 3). With 1 in hand, we explored various conditions to elicit the Cu-catalyzed [3+2] cycloaddition between 1 and benzyl azide (Table 1). In THF with Cu I only starting material Scheme 1. Bromoageliferin, structural inspiration for the synthesis of analogues. TAGE, DHS, and RA-11 are analogues that inhibit and disperse bacterial biofilms. Scheme 2. Design of a 2-AIT. [*] S. A. Rogers, Prof. C. Melander Department of Chemistry North Carolina State University Raleigh, NC 27695-8204 (USA) Fax: (+ 1)919-515-5079 E-mail: christian_melander@ncsu.edu [**] Financial support from NCSU and Agile Sciences, Inc. is gratefully acknowledged. Mass spectra were obtained at the Mass Spec- trometry Laboratory for Biotechnology at NCSU. We thank Dr. Reza A. Ghiladi (NCSU) for spectroscopic assistance. Supporting information for this article (compound synthesis, compound characterization, initial library screening, bacterial growth curves, bacterial colony counts, and dose–response curves) isavailableontheWWWunderhttp://www.angewandte.orgorfrom the author. Angewandte Chemie 5307 Angew. Chem. 2008, 120, 5307–5309 # 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim