Design, synthesis, and evaluation of a novel prodrug, a S-trityl-l-cysteine derivative targeting kinesin spindle protein.

Kinesin spindle protein (KSP) is expressed only in cells undergoing cell division, and hence represents an attractive target for the treatment of cancer. Several KSP inhibitors have been developed and undergone clinical trial, but their clinical use is limited by their toxicity to rapidly proliferating non-cancerous cells. To create new KSP inhibitors that are highly selective for cancer cells, we optimized the amino acid moiety of S-trityl-l-cysteine (STLC) derivative 1 using in silico modeling. Molecular docking and molecular dynamics simulation were performed to investigate the binding mode of 1 with KSP. Consistent with the structure activity relationship studies, we found that a cysteine amino moiety plays an important role in stabilizing the interaction. Based on these findings and the structure of GSH, a substrate of γ-glutamyltransferase (GGT), we designed and synthesized the prodrug N-γ-glutamylated STLC derivative 9, which could be hydrolyzed by GGT to produce 1. The KSP ATPase inhibitory activity of 9 was lower than that of 1, and LC-MS analysis indicated that 9 was converted to 1 only in the presence of GGT in vitro. In addition, the cytotoxic activity of 9 was significantly attenuated in GGT-knockdown A549 cells. Since GGT is overexpressed on the cell membrane of various cancer cells, these results suggest that compound 9 could be a promising prodrug that selectively inhibits the proliferation of GGT-expressing cancer cells.

From UTP to AR-C118925, the discovery of a potent non nucleotide antagonist of the P2Y2 receptor.

The G protein-coupled P2Y2 receptor, activated by ATP and UTP has been reported as a potential drug target for a wide range of important clinical conditions, such as tumor metastasis, kidney disorders, and in the treatment of inflammatory conditions. However, pharmacological studies on this receptor have been impeded by the limited reported availability of stable, potent and selective P2Y2R antagonists. This article describes the design and synthesis of AR-C118925, a potent and selective non-nucleotide antagonist of the P2Y2 receptor discovered using the endogenous P2Y2R agonist UTP as the chemical starting point.

Optimized Target Residence Time: Type†I1/2 Inhibitors for p38α MAP Kinase with Improved Binding Kinetics through Direct Interaction with the R-Spine.

Skepinone-L was recently reported to be a p38α MAP kinase inhibitor with high potency and excellent selectivity in vitro and in vivo. However, this class of compounds still act as fully ATP-competitive Type I binders which, furthermore, suffer from short residence times at the enzyme. We herein describe a further development with the first Type I1/2 binders for p38α MAP kinase. Type I1/2 inhibitors interfere with the R-spine, inducing a glycine flip and occupying both hydrophobic regions I and II. This design approach leads to prolonged target residence time, binding to both the active and inactive states of the kinase, excellent selectivity, excellent potency on the enzyme level, and low nanomolar activity in a human whole blood assay. This promising binding mode is proven by X-ray crystallography.

Synthesis, characterization, and in vitro evaluation of the selective P2Y2 receptor antagonist AR-C118925.

The Gq protein-coupled, ATP- and UTP-activated P2Y2 receptor is a potential drug target for a range of different disorders, including tumor metastasis, inflammation, atherosclerosis, kidney disorders, and osteoporosis, but pharmacological studies are impeded by the limited availability of suitable antagonists. One of the most potent and selective antagonists is the thiouracil derivative AR-C118925. However, this compound was until recently not commercially available and little is known about its properties. We therefore developed an improved procedure for the synthesis of AR-C118925 and two derivatives to allow up-scaling and assessed their potency in calcium mobilization assays on the human and rat P2Y2 receptors recombinantly expressed in 1321N1 astrocytoma cells. The compound was further evaluated for inhibition of P2Y2 receptor-induced ß-arrestin translocation. AR-C118925 behaved as a competitive antagonist with pA 2 values of 37.2 nM (calcium assay) and 51.3 nM (ß-arrestin assay). Selectivity was assessed vs. related receptors including P2X, P2Y, and adenosine receptor subtypes, as well as ectonucleotidases. AR-C118925 showed at least 50-fold selectivity against the other investigated targets, except for the P2X1 and P2X3 receptors which were blocked by AR-C118925 at concentrations of about 1 µM. AR-C118925 is soluble in buffer at pH 7.4 (124 µM) and was found to be metabolically highly stable in human and mouse liver microsomes. In Caco2 cell experiments, the compound displayed moderate permeability indicating that it may show limited peroral bioavailability. AR-C118925 appears to be a useful pharmacological tool for in vitro and in vivo studies.

Dibenzosuberones as p38 mitogen-activated protein kinase inhibitors with low ATP competitiveness and outstanding whole blood activity.

p38α mitogen-activated protein (MAP) kinase is a main target in drug research concerning inflammatory diseases. Nevertheless, no inhibitor of p38α MAP kinase has been introduced to the market. This might be attributed to the fact that there is no inhibitor which combines outstanding activity in biological systems and selectivity. Herein an approach to the development of such inhibitors on the basis of the highly selective molecular probe Skepinone-L is described. Introduction of a "deep pocket" moiety addressing the DFG motif led to an increased activity of the compounds. Hydrophilic moieties, addressing the solvent-exposed area adjacent to hydrophilic region II, conserved a high activity of the compounds in a whole blood assay. Combined with their outstanding selectivity and low ATP competitiveness, these inhibitors are very interesting candidates for use in biological systems and in therapy.

Design, synthesis, and biological evaluation of novel disubstituted dibenzosuberones as highly potent and selective inhibitors of p38 mitogen activated protein kinase.

Synthesis, biological testing, structure-activity relationships (SARs), and selectivity of novel disubstituted dibenzosuberone derivatives as p38 MAP kinase inhibitors are described. Hydrophilic moieties were introduced at the 7-, 8-, and 9-position of the 2-phenylamino-dibenzosuberones, improving physicochemical properties as well as potency. Extremely potent inhibitors were obtained, with half-maximal inhibitory concentration (IC(50)) values in the low nM range in a whole blood assay measuring the inhibition of cytokine release. The high potency of the target compounds together with the outstanding selectivity of this novel class of compounds toward p38 mitogen activated protein (MAP) kinase as compared to other kinases indicate them to be most applicable as tools in pharmacological research and eventually they may foster a new generation of anti-inflammatory drugs.

Novel domino oxidative coupling: C-C bond formation sequence to highly functionalized dibenzo[a,c]cycloheptenes.

A domino sequence involving various MoCl(5)-mediated oxidations followed by trapping and supposed [3,3]-sigmatropic rearrangement provides a fast access to the full carbon skeleton of metasequirin-B. A variety of different moieties R(1) and R(2) are tolerated.

Intramolecular Nicholas reactions in the synthesis of dibenzocycloheptanes. Synthesis of allocolchicine NSC 51046 and analogues and the formal synthesis of (-)-allocolchicine.

The preparation of dibenzocycloheptyne-Co(2)(CO)(6) complexes by intramolecular Nicholas reactions of biaryl-2-propargyl alcohol-Co(2)(CO)(6) derivatives is described. Reductive decomplexation of the dibenzocycloheptyne-Co(2)(CO)(6) complexes affords the corresponding dibenzocycloheptenes, individual members of which have been employed in a formal total synthesis of (-)-allocolchicine, the preparation of 6,7-dihydro-3,4,9,10,11-pentamethoxy-5H-dibenzo[a,c]cyclohepten-5-one, and the enantioselective total syntheses of NSC 51046 and its 3,8,9,10-tetramethoxy regioisomer.

Pt-catalyzed hydrative cyclization of 2-enynylbenzaldehydes and its application to faveline synthesis.

Various 2-[6-en-1-ynyl]benzaldehydes and their analogues were successfully cyclized via Huisgen-type [3+2] cycloaddition to the tetracyclic platinum-carbene complex, which would subsequently undergo hydration to afford the tricyclic products in good yields with excellent stereoselectivities. This hydrative cyclization was also applied to the faveline synthesis.

Synthesis of novel, potentially biologically active dibenzosuberone derivatives.

Novel representatives of the important group of biologically active dibenzosuberone derivatives were prepared: 3,7-dibromo-5-(dimethylaminoethyl- oxyimino)-10,11-dihydro-5H-dibenzo[a,d]cyclohepta-1,4-diene (1), 3,7-dibromo-5-(3- dimethylaminopropylidene)-10,11-dihydro-5H-dibenzo[a,d]cycloheptene (2) and 1,7- dibromo-5-(3-dimethylaminopropylidene)-10,11-dihydro-5H-dibenzo-[a,d]-cycloheptene (3). These compounds are potential tricyclic antidepressants (TCAs), which are still the most frequently prescribed antidepressants in many countries.

Stereochemistry of C-6 nucleophilic displacements on 1,1-difluorocyclopropyldibenzosuberanyl substrates. An improved synthesis of multidrug resistance modulator LY335979 trihydrochloride.

Studies of the displacement chemistry of 1,1-difluorocyclopropyldibenzosuberanyl alcohol 4 and its activated bromide derivative 6 have led to an improved approach to anti-2, a key precursor to LY335979 3HCl (1). Bromination of either syn-4 or anti-4 gave anti-oriented 6, indicating thermodynamically controlled product stereochemistry via a stabilized 1,1-difluorohomotropylium ion intermediate. Reaction of 6 with piperazine proceeded irreversibly to provide an isomeric mixture of piperazine products, with the syn:anti product ratio increased by solvent effects. Reaction of 6 with pyridine and pyrazine, on the other hand, gave anti-pyridinium and pyrazinium salts, respectively, apparently via equilibration of initially formed syn products. Reduction of pyrazinium salt 11 with lithium borohydride/TFA provided anti-2 unaccompanied by its syn isomer. A practical and expeditious approach to 1 was derived from these new results.

Tricyclic alkylamides as melatonin receptor ligands with antagonist or inverse agonist activity.

This work reports the design and synthesis of novel alkylamides, characterized by a dibenzo[a,d]cycloheptene nucleus, as melatonin (MLT) receptor ligands. The tricyclic scaffold was chosen on the basis of previous quantitative structure-activity studies on MT1 and MT2 antagonists, relating selective MT2 antagonism to the presence of an aromatic substituent out of the plane of the MLT indole ring. Some dibenzo seven-membered structures were thus selected because of the noncoplanar arrangement of their benzene rings, and an alkylamide chain was introduced to fit the requirements for MLT receptor binding, namely, dibenzocycloheptenes with an acylaminoalkyl side chain at position 10 and dibenzoazepines with this side chain originating from the nitrogen atom bridging the two phenyl rings. Binding affinity at human cloned MT1 and MT2 receptors was measured by 2-[125I]iodomelatonin displacement assay and intrinsic activity by the GTPgammaS test. The majority of the compounds were characterized by higher affinity at the MT2 than at the MT1 receptor and by very low intrinsic activity values, thus confirming the importance of the noncoplanar arrangement of the two aromatic rings for selective MT2 antagonism. Dibenzocycloheptenes generally displayed higher MT1 and MT 2affinity than dibenzoazepines. N-(8-Methoxy-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-10-ylmethyl)propionamide (4c) and -butyramide (4d) were the most selective MT2 receptor antagonists of the series, with MT2 receptor affinity comparable to that of melatonin and as such among the highest reported in the literature for MLT receptor antagonists. The acetamide derivative 4b produced a noticeable reduction of GTPgammaS binding at MT2 receptor, thus being among the few inverse agonists described.

Structural properties of dibenzosuberanylpiperazine derivatives for efficient reversal of chloroquine resistance in Plasmodium chabaudi.

For the purpose of developing chemosensitizers to reverse chloroquine (CQ) resistance in Plasmodium chabaudi in vivo, dibenzosuberanylpiperazine (1-(10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-yl)piperazine) (DSP) and its piperazin-1-yl derivatives were synthesized systematically. DSP hydrochloride (3) was obtained from the reaction of dibenzosuberanyl chloride with piperazine in the presence of 1,8-diazabicyclo[5,4,0]-7-undecene (DBU). To understand the relationship between the substituent patterns of DSP derivatives and their biological activities, 13 hydroxyalkyl or hydroxyalkenyl derivatives were synthesized by an attack of the piperazine secondary amine of 3 on commercially available epoxides in the presence of triethylamine or DBU, and three alkyl or alkynyl derivatives were synthesized by the reactions of 3 with the corresponding organic chlorides in the presence of DBU. In both reactions, the yield was a maximum of 90%. The biological activities of the synthesized compounds were evaluated on the basis of two values: antimalarial activity and reversal activity. The values of antimalarial activities by single administration of 17 test compounds were not effective, being in the range 67-152% on day 4 after infection of Plasmodium chabaudi to mice except for the administration of 3-(dibenzosuberanylpiperazin-1-yl)-1-butene (29, 22%). On the other hand, administration of the seven test compounds (50 mg/kg dose) combined with CQ (3-4 mg/kg) gave high reversal activities, namely, low values (0% on day 4). The effective test compounds were those obtained by introducing the following substituents: 2-hydroxybutyl (24), 2-hydroxyhexen-5-yl (27), 2-hydroxybuten-3-yl (28a), 2-substituted 1-hydroxybuten-3-yl (28b), 4-acetoxybutyn-2-yl (30), 4-hydroxybutyn-2-yl (31), and 3-substituted buten-1-yl (29), which correspond to the nonbulky groups of hydroxyalkyl (C4), hydroxyalkenyl (C4-C6), hydroxyalkynyl (C4), or alkenyl (C4). These results may lead to the development of an approach to developing clinically applicable chemosensitizers for drug-resistant malaria.

Novel angiotensin II receptor antagonists. Design, synthesis, and in vitro evaluation of dibenzo[a,d]cycloheptene and dibenzo[b,f]oxepin derivatives. Searching for bioisosteres of biphenylyltetrazole using a three-dimensional search technique.

Three-dimensional substructure searching (3D search), using the program MACCS-3D, was utilized for designing novel angiotensin II receptor antagonists which contain a bioisostere of the biphenylyltetrazole moiety of DuP 753. A 3D query was prepared from an overlay model of substructures of several potent AII antagonists. The search system retrieved 139 compounds from the database MDDR-3D, which consisted of 29,400 medicinal patent compounds. A tricyclic compound was selected from the retrieved compounds and then evolved by considering steric fitness to the overlay model and synthetic feasibility. Finally, various novel AII antagonists having dibenzo[a,d]cycloheptene or dibenzo[b,f]oxepin were designed and synthesized. The receptor binding activity (Ki) for several members of this series was in the 10(-10) M range, demonstrating the ability of 3D search technique to explore new lead structures.

10,5-(Iminomethano)-10,11-dihydro-5H-dibenzo[a,d]cycloheptene and derivatives. Potent PCP receptor ligands.

IDDC (3, 10,5-(iminomethano)-10,11-dihydro-5H-dibenzo[a,d]cycloheptene++ +) and a series of substituted derivatives were synthesized and evaluated in vitro for their ability to displace tritiated MK-801 ([3H]-2) from its specific binding site in guinea pig brain homogenate. Substitution at the 3-position of 3 with bromine, chlorine, and fluorine led to increased binding affinity. In contrast, substitution of donor groups at the 3-position gave decreased binding affinities, as did all substitutions at the 7-position and on nitrogen. Where racemic mixtures were resolved, the (+)-optical antipodes were more active than their enantiomers or racemates. The most active ligand found in this study was (+)-13e (IC50 = 15.5 +/- 4.5 nM). The affinity of (+)-13e for the PCP receptor makes it among the most potent ligands known. In vitro neuroprotection was demonstrated by 3, (+)-3, and (+)-6 (N-Me-IDDC) against glutamate-induced cell death in rat hippocampal cells.

A novel photoaffinity ligand for the phencyclidine site of the N-methyl-D-aspartate receptor labels a Mr 120,000 polypeptide.

A radiolabeled photoaffinity ligand has been developed for the N-methyl-D-aspartate (NMDA)-preferring excitatory amino acid receptor complex. [3H]3-Azido-(5S, 10R)(+)-5-methyl-10,11-dihydro-5H- dibenzo[a,d]cyclohepten-5,10-imine [3H]3-azido-MK-801 demonstrated nearly identical affinity, density of binding sites, selectivity, pH sensitivity, and pharmacological profile in reversible binding assays with guinea pig brain homogenates to those displayed by its parent compound, MK-801. When employed in a photo-labeling protocol designed to optimize specific incorporation, [3H]3-azido-MK-801 labeled a single protein band which migrated in sodium dodecyl sulfate-polyacrylamide gels with Mr = 120,000. Incorporation of tritium into this band was completely inhibited when homogenates and [3H]3-azido-MK-801 were coincubated with 10 microM phencyclidine. These data suggest that the phencyclidine site of the NMDA receptor complex is at least in part comprised of a Mr = 120,000 polypeptide.

Structure and activity of hydrogenated derivatives of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801).

Several hydrogenated derivatives of the potent NMDA antagonist 1 have been prepared and evaluated as competitive inhibitors of [3H]-1 binding. These compounds were also tested for their ability to act as noncompetitive antagonists of NMDA in vitro. These studies indicate that two aromatic rings are not strictly required for high-affinity binding or NMDA antagonism.

Synthesis and structure-activity relationship of C5-substituted analogues of (+-)-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine [(+-)-desmethyl-MK801]: ligands for the NMDA receptor-coupled phencyclidine binding site.

A series of eight C5-substituted analogues of (+-)-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (1) have been prepared by the directed lithiation-alkylation (and acylation) of its (+-)-N-tert-butylformamidinyl derivative 2 followed by formamidine solvolysis. An additional 10 analogues were prepared by elaboration of the C5-ethyl ester derivative. Analogues possessing large (e.g. propyl and larger) lipophilic substituents displace [3H]-1-(1-thienylcyclohexyl)piperidine [( 3H]TCP) from the high-affinity phencyclidine (PCP) binding site in rat brain homogenates only at high concentrations (Ki greater than 1000 nM); however, the presence of a polar amino functionality (e.g. 2-aminoethyl) offsets this effect (Ki = 20 nM). Thus, the boundary condition for lipophilic substituents larger than ethyl appears to be polar in nature. Interaction of the 11 relatively small (MR less than 14) C5-substituted analogues of 1 with the high-affinity PCP binding site associated with the N-methyl-D-aspartate (NMDA) receptor is best described by the equation log (1/Ki) = -5.83F + 0.64 pi + 7.41 (r = 0.90).

Synthesis of 11C-labeled (+-)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imin e [(+-)-[11C]MK801].

The synthesis of C5 labeled (+-)-5-[11C]methyl-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten- 5,10-imine [(+-)-[11C]MK801] has been accomplished via alkylation of (+-)-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten-5,10-imine-N-t- butylformamidine [(+-)-5-des-methyl MK801 formamidine). The 11C labeling is accomplished by reaction of the anion of (+-)-5-des-methyl MK801 formamidine, generated with s-butyllithium, and [11C]methyl iodide.