Structure-activity relationships of furanones, dihydropyrrolones and thiophenones as potential quorum sensing inhibitors.

Since their initial isolation from the marine alga Delisea pulchra, bromofuranones have been investigated as potential inhibitors of quorum sensing (QS) in various bacterial strains. QS is an important mechanism by which bacteria co-ordinate their molecular response to the environment. QS is intrinsically linked to bacterial antibiotic resistance. Inspired by nature, chemists have developed a wide variety of synthetic analogs in an effort to elucidate the structure-activity relationships of these compounds, and to ultimately develop novel antimicrobial agents. In this work, we describe advances in this field while paying particular attention to apparent structure-activity relationships. This review is organized according to the main ring systems under investigation, namely furanones, dihydropyrrolones and thiophenones.

Environmental fate and effects of novel quorum sensing inhibitors that can control biofilm formation.

The formation of bacterial biofilms can have negative impacts on industrial processes and are typically difficult to control. The increase of antibiotic resistance, in combination with the requirement for more environmentally focused approaches, has placed pressure on industry and the scientific community to reassess biofilm control strategies. The discovery of bacterial quorum sensing, as an important mechanism in biofilm formation, has led to the development of new substances (such as halogenated thiophenones) to inhibit the quorum sensing process. However, there are currently limited data regarding the biodegradability or ecotoxicity of these substances. To assess the environmental fate and effects of thiophenones capable of quorum sensing inhibition, candidate substances were first identified that have potentially high biodegradability and low ecotoxicity using quantitative structure activity relationships. Subsequent confirmatory hazard assessment of these substances, using a marine alga and a marine crustacean, indicated that these estimates were significantly under predicted with acute toxicity values more than three orders of magnitude lower than anticipated combined with limited biodegradability. Therefore, although these quorum sensing inhibitors appear a promising approach to control biofilms, they may also have environmental impacts on certain aquatic organisms.

Crystal structure of ethyl 2-amino-4-(4-chloro-phen-yl)-4H-1-benzothieno[3,2-b]pyran-3-carboxyl-ate.

The title compound, C20H16ClNO3S, is built up from three fused rings, one five- and two six-membered rings, linked to a 3-eth-oxy-carbonyl group and to a 4-chloro-phenyl ring. The hydropyran ring has a flattened envelope conformation, with the C atom substituted by the 4-chloro-phenyl ring as the flap (displaced by 0.077 (2) Šfrom the plane through the other atoms). The fused three-ring system is quasi-planar (r.m.s. deviation = 0.057 Å), with the largest deviation from the mean plane being 0.106 (1) Šfor the C atom substituted by the 4-chloro-phenyl ring. The 4-chloro-phenyl ring is approximately perpendicular to the mean plane of the fused ring system, as indicated by the dihedral angle of 77.32 (6)° between their mean planes. There is an intra-molecular N-H⋯O hydrogen bond forming an S(6) ring motif. In the crystal, mol-ecules are linked by pairs of N-H⋯O hydrogen bonds, forming inversion dimers with an R 2 (2)(12) ring motif. There are also short inter-molecular Cl⋯O inter-actions present [3.1226 (12) Å] between neighbouring mol-ecules.