Design, synthesis and biological characterization of selective LIMK inhibitors.

Inhibitors of LIM kinases are considered of interest for several indications, including elevated intraocular pressure (IOP), cancer, or infection by HIV-1. LX-7101 (Lexicon Pharmaceuticals) was advanced to Phase-I clinical trials as an IOP-lowering agent for treatment of glaucoma. We here discuss the design, synthesis and evaluation of LIMK inhibitors based on a pyrrolopyrimidine scaffold, which represent close analogs of LX-7101. Exploration of structure-activity relationships revealed that many of such compounds, including LX-7101, cause potent inhibition of LIMK1 and LIMK2, and also ROCK2 and PKA. Molecular variations around the various structural elements of LX-7101 were attempted. Substitution on position 6 of the pyrrolopyrimidine scaffold led to the identification of LX-7101 analogs displaying good selectivity versus ROCK, PKA and Akt.

Novel Roflumilast analogs as soft PDE4 inhibitors.

PDE4 inhibitors are of high interest for treatment of a wide range of inflammatory or autoimmune diseases. Their potential however has not yet been realized due to target-associated side effects, resulting in a low therapeutic window. We herein report the design, synthesis and evaluation of novel PDE4 inhibitors containing a γ-lactone structure. Such molecules are designed to undergo metabolic inactivation when entering circulation, thereby limiting systemic exposure and reducing the risk for side effects. The resulting inhibitors were highly active on both PDE4B1 and PDE4D2 and underwent rapid degradation in human plasma by paraoxonase 1. In contrast, their metabolites displayed markedly reduced permeability and/or on-target activity.

3-[2-(Aminomethyl)-5-[(pyridin-4-yl)carbamoyl]phenyl] benzoates as soft ROCK inhibitors.

Clinical development of ROCK inhibitors has so far been limited by systemic or local ROCK-associated side effects. A soft drug approach, which involves predictable metabolic inactivation of an active compound to a nontoxic metabolite, could represent an attractive way to obtain ROCK inhibitors with improved tolerability. We herein report the design and synthesis of a new series of soft ROCK inhibitors structurally related to the ROCK inhibitor Y-27632. These inhibitors contain carboxylic ester moieties which allow inactivation by esterases. While the parent esters display strong activity in enzymatic (ROCK2) and cellular (MLC phosphorylation) assays, their corresponding carboxylic acid metabolites have negligible functional activity. Compound 32 combined strong efficacy (ROCK2 IC50=2.5 nM) with rapid inactivation in plasma (t1/2 <5'). Compound 32 also demonstrated in vivo efficacy when evaluated as an IOP-lowering agent in ocular normotensive New-Zealand White rabbits, without ocular side effects.

Anticonvulsant activity of bisabolene sesquiterpenoids of Curcuma longa in zebrafish and mouse seizure models.

Turmeric, obtained from the rhizomes of Curcuma longa, is used in South Asia as a traditional medicine for the treatment of epilepsy. To date, in vivo studies on the anticonvulsant activity of turmeric have focused on its principal curcuminoid, curcumin. However, poor absorption and rapid metabolism have limited the therapeutic application of curcumin in humans. To explore the therapeutic potential of turmeric for epilepsy further, we analyzed its anticonvulsant activity in a larval zebrafish seizure assay. Initial experiments revealed that the anticonvulsant activity of turmeric in zebrafish larvae cannot be explained solely by the effects of curcumin. Zebrafish bioassay-guided fractionation of turmeric identified bisabolene sesquiterpenoids as additional anticonvulsants that inhibit PTZ-induced seizures in both zebrafish and mice. Here, we present the first report of the anticonvulsant properties of bisabolene sesquiterpenoids and provide evidence which warrants further investigation toward the mechanistic understanding of their neuromodulatory activity.

2-(4-Meth-oxy-benz-yl)-4,6-diphenyl-2,5-diaza-bicyclo-[2.2.2]oct-5-en-3-one.

In the crystal structure of the title compound, C(26)H(24)N(2)O(2), weak inter-molecular C-H⋯π inter-actions involving the benzene of the p-methoxy benzyl group and one of the phenyl rings result in the formation of chains consisting of alternating enanti-omers. Weak C-H ⋯O inter-actions with the methoxy O atom lead to the formation of layers, which are inter-linked by further C-H⋯O inter-actions into a three-dimensional assembly.

Fragment-Based Discovery of Novel Potent Sepiapterin Reductase Inhibitors.

Genome-wide-association studies in chronic low back pain patients identified sepiapterin reductase as a high interest target for developing new analgesics. Here we used 19F NMR fragment screening for the discovery of novel, ligand-efficient SPR inhibitors. We report the crystal structures of six chemically diverse inhibitors complexed with SPR, identifying relevant interactions and binding modes in the sepiapterin pocket. Exploration of our initial fragment screening hit led to double-digit nanomolar inhibitors of SPR with excellent ligand efficiency.

3-Benzyl-5-bromo-pyrazin-2(1H)-one.

In the title compound, C(11)H(9)BrN(2)O, the mol-ecules are linked into R(2) (2)(8) dimers by paired N-H⋯O hydrogen bonds and these dimers are further stacked into columns along the c axis by π-π inter-actions between pyrazinone rings [centroid-centroid distance = 3.544 Å; the dihedral angle between the planes of these rings is 7.51 (16)°]. The title compound is a precursor for agents with potential use as pharmaceuticals.

trans-Chlorido[6-chloro-4-(4-methoxy-benz-yl)-3-oxo-3,4-dihydro-pyrazin-2-yl]-bis-(triphenyl-phosphine)palladium(II).

The title compound, [Pd(C(12)H(10)ClN(2)O(2))Cl(C(18)H(15)P)(2)], is the inter-mediate of the reduction of a 3,5-dichloro-pyrazinone [Loosen, Tutonda, Khorasani, Compernolle & Hoornaert (1991 ▶). Tetra-hedron, 47, 9259-9268]. This species is formed by oxidative addition of coordinatively unsaturated Pd(0) to the reactive 3-position of the heterocycle. The coordination around the Pd atom is square planar, with two trans PPh(3) ligands. π-π inter-actions are observed between the centroid of the pyrazinone ring and planes of two adjacent phenyl rings, one from each PPh(3) group (3.25 and 3.078 Å), stabilizing the inter-mediate structure. This could explain the reduced reactivity towards substitution of the Cl atom by the formate anion, resulting in poor yield of the reduced compound. 3-Substituted pyrazinones are important precursors in the synthesis of 5-amino-piperidinone-2-carboxyl-ate (APC) systems.

Design, synthesis, and biological evaluation of novel, highly active soft ROCK inhibitors.

ROCK1 and ROCK2 play important roles in numerous cellular functions, including smooth muscle cell contraction, cell proliferation, adhesion, and migration. Consequently, ROCK inhibitors are of interest for treating multiple indications including cardiovascular diseases, inflammatory and autoimmune diseases, lung diseases, and eye diseases. However, systemic inhibition of ROCK is expected to result in significant side effects. Strategies allowing reduced systemic exposure are therefore of interest. In a continuing effort toward identification of ROCK inhibitors, we here report the design, synthesis, and evaluation of novel soft ROCK inhibitors displaying an ester function allowing their rapid inactivation in the systemic circulation. Those compounds display subnanomolar activity against ROCK and strong differences of functional activity between parent compounds and expected metabolites. The binding mode of a representative compound was determined experimentally in a single-crystal X-ray diffraction study. Enzymes responsible for inactivation of these compounds once they enter systemic circulation are also discussed.

Artemisinin analogues as potent inhibitors of in vitro hepatitis C virus replication.

We reported previously that Artemisinin (ART), a widely used anti-malarial drug, is an inhibitor of in vitro HCV subgenomic replicon replication. We here demonstrate that ART exerts its antiviral activity also in hepatoma cells infected with full length infectious HCV JFH-1. We identified a number of ART analogues that are up to 10-fold more potent and selective as in vitro inhibitors of HCV replication than ART. The iron donor Hemin only marginally potentiates the anti-HCV activity of ART in HCV-infected cultures. Carbon-centered radicals have been shown to be critical for the anti-malarial activity of ART. We demonstrate that carbon-centered radicals-trapping (the so-called TEMPO) compounds only marginally affect the anti-HCV activity of ART. This provides evidence that carbon-centered radicals are not the main effectors of the anti-HCV activity of the Artemisinin. ART and analogues may possibly exert their anti-HCV activity by the induction of reactive oxygen species (ROS). The combined anti-HCV activity of ART or its analogues with L-N-Acetylcysteine (L-NAC) [a molecule that inhibits ROS generation] was studied. L-NAC significantly reduced the in vitro anti-HCV activity of ART and derivatives. Taken together, the in vitro anti-HCV activity of ART and analogues can, at least in part, be explained by the induction of ROS; carbon-centered radicals may not be important in the anti-HCV effect of these molecules.

Synthesis of 2(1H)-pyrazinone phosphonates via an Arbuzov-type reaction.

A simple and catalyst-free method for the synthesis of phosphonated 2(1H)-pyrazinones is described starting from 3,5-dichloropyrazinones. The method also works for 3-bromo- and 3-iodopyrazinones. Classical heating conditions as well as microwave-enhanced reaction conditions were tested.