Publications by authors named "Shingo Fujioka"

A number of RORγ inhibitors have been reported over the past decade. There were also several examples advancing to human clinical trials, however, none of them has reached the market yet, suggesting that there could be common obstacles for their future development. As was expected from the general homology of nuclear receptor ligands, insufficient selectivity as well as poor physicochemical properties were identified as potential risks for a RORγ program.

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Tyrosine phosphorylation is an essential post-translational modification that regulates various biological events and is implicated in many diseases including cancer and atherosclerosis. Vascular endothelial protein tyrosine phosphatase (VE-PTP), which plays an important role in vascular homeostasis and angiogenesis, is therefore an attractive drug target for these diseases. However, there are still no drugs targeting PTP including VE-PTP.

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A fragment-based lead discovery approach was applied to Pyruvate Dehydrogenase Kinases (PDHKs) to discover inhibitors against the ATP binding site with novel chemotypes. X-ray fragment screening toward PDHK4 provided a fragment hit 1 with a characteristic interaction in a deep pocket of the ATP binding site. While known inhibitors utilize several water molecules in a deep pocket to form water-mediated hydrogen bond interactions, the fragment hit binds deeper in the pocket with a hydrophobic group.

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A novel unsymmetrical structural class of orally bioavailable hepatitis C virus (HCV) nonstructural 5A protein (NS5A) inhibitors has been generated by improving both the solubility and membrane permeability of the lead compound found in our previous work. The representative compound 14, with a 5-hydroxymethylpyrazine group and a 3-t-butylpropargyl group on each side of the molecule, exhibited the best oral bioavailability in this study, inhibiting not only the HCV genotype 1a, 1b, 2a, and 3a replicons with EC values in the picomolar range, but also inhibited 1a Q30 mutants induced by launched symmetrical inhibitors with EC values in the low nanomolar range.

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A novel unsymmetrical structural class of HCV NS5A inhibitors showing picomolar range antiviral activity has been identified. An unsymmetrical lead compound 2, generated from a substructure of a known symmetrical inhibitor 1, was optimized by extension of its substituents to interact with the hitherto unexplored site of the target protein. This approach afforded novel highly potent unsymmetrical inhibitor 20, which not only equally inhibited HCV genotypes1a, 1b, and 2a with EC values in the picomolar range, but also inhibited the 1a Q30K mutant induced by a launched symmetrical inhibitor daclatasvir with an EC in the low nanomolar range.

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Starting from a previously reported RORγ inhibitor (1), successive efforts to improve in vivo potency were continued. Introduction of metabolically beneficial motifs in conjunction with scaffold hopping was examined, resulting in discovery of the second generation RORγ inhibitor composed of a 4-(isoxazol-3-yl)butanoic acid scaffold (24). Compound 24 achieved a 10-fold improvement in in vivo potency in a mouse CD3 challenge model along with significant anti-inflammatory effects in a mouse dermatitis model.

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[reaction, structure: see text] Conjugate addition of various prochiral nitroalkanes to cyclic alpha,beta-unsaturated ketones was found to be efficiently catalyzed by N-spiro C2-symmetric chiral quaternary ammonium bromide 1b possessing a 3,5-bis(3,4,5-trifluorophenyl)phenyl substituent under solid-liquid phase-transfer conditions to afford the corresponding gamma-nitro ketones in excellent chemical yields with unprecedented levels of diastereo- and enantiocontrol.

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Highly enantioselective conjugate addition of nitroalkanes to alkylidenemalonates has been accomplished for the first time by the utilization of efficient phase-transfer catalysis of N-spiro C2-symmetric chiral quaternary ammonium bromide 1. For instance, simple mixing of nitropropane (2, R1 = Et), diisopropyl benzylidienemalonate (3, R2 = Ph), Cs2CO3 (1 equiv), and (S,S)-1 (1 mol %) in toluene at 0 degrees C for 2.5 h gave rise to the desired conjugate addition product 4 (R1 = Et, R2 = Ph) quantitatively (anti/syn = 86:14) with 97% ee (anti isomer).

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Direct catalytic asymmetric Michael addition reactions of ketones to nitroolefins using newly developed chiral pyrrolidine-pyridine conjugate bases as catalysts are described. The desired 1,4-adducts are obtained in excellent yields with high enantio- and diastereoselectivities.

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