Microwave and flow syntheses of Pseudomonas quinolone signal (PQS) and analogues.

Expedient syntheses of Pseudomonas quinolone signal (PQS) and related structural analogues using microwave and flow methods are reported.

Discovery of a quorum sensing modulator pharmacophore by 3D small-molecule microarray screening.

The screening of large arrays of drug-like small-molecules was traditionally a time consuming and resource intensive task. New methodology developed within our laboratories provides an attractive low cost, 3D microarray-assisted screening platform that could be used to rapidly assay thousands of compounds. As a proof-of-principle the platform was exploited to screen a number of quorum sensing analogs. Quorum sensing is used by bacterium to initiate and spread infection; in this context its modulation may have significant clinical value. 3D microarray slides were probed with fluorescently labeled ligand-binding domains of the LuxR homolog CarR from Erwinia carotovora subsp. carotovora. The 3D microarray platform was used to discover the biologically active chloro-pyridine pharmacophore, which was validated using a fluorometric ligand binding assay and ITC. Analogs containing the chloro-pyridine pharmacophore were found to be potent inhibitors of N-acyl-homoserine-lactone (AHL) mediated quorum sensing phenotypes in Serratia (IC(50) = ∼5 µM) and Pseudomonas aeruginosa (IC(50) = 10-20 µM).

Continuous flow based catch and release protocol for the synthesis of alpha-ketoesters.

Using a combination of commercially available mesofluidic flow equipment and tubes packed with immobilised reagents and scavengers, a new synthesis of alpha-ketoesters is reported.

Fluorous tagged small molecule microarrays.

The affinity fluorous interaction between fluorous tagged small molecules and a fluoroalkyl modified glass surface was shown to facilitate the detection of protein-ligand binding interactions in the fabrication and screening of small molecule microarrays.

Immunomodulatory effects of Pseudomonas aeruginosa quorum sensing small molecule probes on mammalian macrophages.

Pseudomonas aeruginosa produces the quorum sensing signalling molecule N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL). This natural product not only coordinates production of virulence factors by the bacterium, but also has immunomodulatory effects on the host organism. Immunomodulatory small molecules are valuable for immunology research and are potential therapeutics for autoimmune diseases such as rheumatoid arthritis, and immunosuppressive drugs following organ transplants. We describe the total synthesis of OdDHL using solid-supported reagents and scavengers, which has the potential to be used for automated analogue synthesis. OdDHL and four analogues were tested for their ability to activate or inhibit release of the pro-inflammatory mediators tumour necrosis factor alpha (TNFalpha) and nitric oxide (NO) from equine or murine macrophages (immune cells). Two of the analogues showed substantial immunomodulatory activity with these macrophages. One analogue showed differing species selectivity, being a potent antagonist in mouse cells, but a partial agonist in horse-derived macrophages. These compounds have the therapeutic potential to be used for protecting animals from bacterial septic shock.

The use of a continuous flow-reactor employing a mixed hydrogen-liquid flow stream for the efficient reduction of imines to amines.

Imines have been reduced to amines in high yield, and with excellent chemoselectivity, by catalytic hydrogenation in a continuous flow-reactor, utilising an electrochemically-generated hydrogen source to produce a mixed hydrogen-liquid flow stream.

Automated parallel, multi-step polymer-assisted solution phase (PASP) synthesis of substituted benzimidazole derivatives.

The automated polymer-assisted solution phase (PASP) synthesis of a 72 member library of 2-alkylthio-benzimidazoles 16 and benzimidazolin-2-ones 17 using commercially available robotic workstations is described. By incorporating both automated aqueous work-ups, in-line scavenging and 'catch and release' protocols the desired compounds were obtained directly in good yields and excellent purities without the need for conventional chromatographic purification. The synthesis described demonstrates how both manual and automated equipment may be utilised together to provide a versatile approach that facilitates parallel compound synthesis.

Solid-phase synthesis of apicidin A and a cyclic tetrapeptoid analogue.

The solid-phase synthesis of the antiprotozoal cyclic tetrapeptide apicidin A is reported and its synthetic accessibility is contrasted with that of a structurally similar reduced cyclic tetrapeptoid analogue.

Novel synthesis of fused isoxazolidines via a palladium catalysed allene insertion-intramoleculer 1,3-dipolar cycloaddition cascade reaction.

A one pot, three component palladium catalysed allenation of aryl iodides, in combination with a nitrone cycloaddition, leads to formation of fused isoxazolidines, creating two rings, two stereocentres and one tetrasubstituted carbon centre.

Wavelength dependent photo-controlled differential release of compounds from solid phase resin.

A method to effect photo-mediated differential release of bead-based compound libraries using a tuneable laser in combination with chromatically orthogonal photolabile linkers is described.

3D small-molecule microarrays.

A PEG based 3D hydrogel slide was developed specifically for small-molecule microarraying purposes, which displayed improved loading capacity, signal sensitivity and spot morphology compared with a commercially available slide and comparative 2D slide.

Small-molecule screening: advances in microarraying and cell-imaging technologies.

Cell-permeable small molecules can be used to modulate protein function selectively, rapidly, reversibly, and conditionally with temporal and quantitative control in biological systems. The identification of these chemical probes can require the screening of large numbers of small molecules. With the advent of new technologies, small-molecule high-throughput screening is widely available. This Review focuses on the emerging technologies of microarray screening platforms and high-content screening formats.

Fully automated flow-through synthesis of secondary sulfonamides in a binary reactor system.

A fully automated flow-through process for the production of secondary sulfonamides is presented. Primary sulfonamides were monoalkylated using a two-step "catch and release" protocol to generate library products of high purity. The automated flow synthesis platform incorporates four independent reactor columns and is able to perform automated column regeneration. A 48-member sulfonamide library was prepared as two 24-member sublibraries, affording library compounds in good yields and high purities without the need for further column chromatographic purification.

A highly automated, polymer-assisted strategy for the preparation of 2-alkylthiobenzimidazoles and N,N'-dialkylbenzimidazolin-2-ones.

A multistep, polymer-assisted solution phase strategy for the highly automated (auto-PASP) synthesis of 2-alkylthiobenzimidazole and N,N'-dialkylbenzimidazolin-2-one libraries is presented. The approach incorporates in-line purification techniques to afford library products directly with high purities and is exemplified by the preparation of a 96-member 2-alkylthiobenzimidazoline library 1[1-12,1-8] and a 72-member N,N'-dialkylbenzimidazolin-2-one library 9[1-12,1-6].

Practical synthesis of a dithiane-protected 3',5'-dialkoxybenzoin photolabile safety-catch linker for solid-phase organic synthesis.

The solution-phase preparation of the 3',5'-dialkoxybenzoin photolabile safety-catch linker 16 is described. Pivotal to this convenient synthesis is the selection of appropriate orthogonal protecting groups for the alkoxy functionalities present. The new linker can be readily loaded onto any standard amine-terminating resin under peptide-coupling conditions, without the need to protect the secondary alcohol functionality, and subsequently loaded with substrate. Alternatively, the loading efficiency of sterically hindered substrates can be enhanced by preloading the semiprotected linker variant 10 in solution prior to immobilization onto the resin. This second generation of benzoin photolabile safety-catch linkers provides greater control of both linker loading and resin attachment and should prove to be a more versatile and convenient form of the linker.

Studies on the chemical stability and functional group compatibility of the benzoin photolabile safety-catch linker using an analytical construct.

A chemical stability study of the benzoin photolabile safety-catch linker (BPSC) has been carried out using a dual-linker analytical construct to establish its compatibility with a range of commonly employed solid-phase reaction conditions. As a result of this study, the dithiane-protected benzoin linker was shown to be reactive only toward strong acids and fluoride nucleophile. Furthermore, a scan of diverse functional groups thought to be unstable toward the safety-catch removal conditions has also been carried out. These data should provide assistance in future utilization of the BPSC for syntheses.

A novel anthracenyl tagged protecting group for "phase-switching" applications in parallel synthesis.

A new "phase-switching" protecting group 1 that facilitates the parallel synthesis of carboxylic acids, esters, and carboxamides is described. Its use permits chemistries to be performed in solution, which may be conveniently monitored with conventional analytical techniques, followed by subsequent immobilization onto a solid-phase support to aid compound purification. Carboxylic acids, esters, and carboxamides are then cleaved from the solid support following activation of the "safety-catch" and treatment with the desired nucleophile.

Convenient preparation and use of a new analytical construct for the analysis and development of solid-phase chemistries.

An expedient and scalable synthesis of a versatile new analytical construct intermediate 1 is described. The utility of the intermediate 1 is exemplified by the preparation of the construct resin 14 incorporating an acid-labile linker which is used to conveniently develop optimized conditions leading to the preparation of a small compound array 24(1-3,1-3). The optimized conditions are shown to work equally well on both the construct resin 14 and the corresponding base resin 15.

The development and preparation of the 2,4-dimethoxybenzyl arylhydrazine (DMBAH) "latent" safety-catch linker: solid phase synthesis of ketopiperazines.

The development and preparation of the 2,4-dimethoxybenzyl arylhydrazine (DMBAH) linker 3, a new class of "latent" safety-catch linker which is stable under Mitsunobu alkylation conditions and in the presence of amines and hydrazine, is reported. The utility of the new linker is exemplified by the synthesis of ketopiperazines (MKPs) 24 bearing up to four points of diversity using a cyclitive cleavage approach.