Many proteobacteria are able to monitor their population densities through the release of pheromones known as N-acylhomoserine lactones. At high population densities, these pheromones elicit diverse responses that include bioluminescence, biofilm formation, production of antimicrobials, DNA exchange, pathogenesis and symbiosis. Many of these regulatory systems require a pheromone-dependent transcription factor similar to the LuxR protein of Vibrio fischeri. Here we present the structure of a LuxR-type protein. TraR of Agrobacterium tumefaciens was solved at 1.66 A as a complex with the pheromone N-3-oxooctanoyl-L-homoserine lactone (OOHL) and its TraR DNA-binding site. The amino-terminal domain of TraR is an alpha/beta/alpha sandwich that binds OOHL, whereas the carboxy-terminal domain contains a helix turn helix DNA-binding motif. The TraR dimer displays a two-fold symmetry axis in each domain; however, these two axes of symmetry are at an approximately 90 degree angle, resulting in a pronounced overall asymmetry of the complex. The pheromone lies fully embedded within the protein with virtually no solvent contact, and makes numerous hydrophobic contacts with the protein as well as four hydrogen bonds: three direct and one water-mediated.

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We describe a novel series of potent inhibitors of human beta-secretase. These compounds possess the hydroxyethyl amine transition state isostere. A 2.5A crystal structure of inhibitor 32 bound to BACE is provided.

We recently described a novel series of aminopyridopyrazinones as PDE5 inhibitors. Efforts toward optimization of this series culminated in the identification of 3-[4-(2-hydroxyethyl)piperazin-1-yl]-7-(6-methoxypyridin-3-yl)-1-(2-propoxyethyl)pyrido[3,4-b]pyrazin-2(1H)-one, which possessed an excellent potency and selectivity profile and demonstrated robust in vivo blood pressure lowering in a spontaneously hypertensive rat (SHR) model. Furthermore, this compound is brain penetrant and will be a useful agent for evaluating the therapeutic potential of central inhibition of PDE5. This compound has recently entered clinical trials.

A solid-phase organic synthesis method has been developed for the preparation of 3-carboxypyrrolinones 9. Treatment of polymer-bound malonic acid with amino alcohols afforded the malonamide resin products 6. Benzyl and alkyl amino alcohols were prepared in solution via a two-step procedure without purification and were coupled to the resin directly using a resin capture strategy. Polymer loadings and product conversions were determined by direct cleavage of resin-bound materials and analysis by 1H NMR spectroscopy with an internal standard. Treatment of the polymer-bound malonamides with TFA released the malonamic acids, 10, which underwent further reaction to afford the trifluoroacetate derivatives 11. Secondary amides underwent an additional cyclization to afford oxazoles 12. The malonamide resins 6 can be oxidized to the corresponding ketones 7 by treatment with CrO2(O-t-Bu)2, which can in turn be cyclized in the presence of LDA or LHMDS to afford the carboxypyrrolinones 8. TFA treatment releases the free carboxypyrrolinones, 9, in 43−80% overall yield.