Primary Amine Nucleophilic Addition to Nitrilium Closo-Dodecaborate [B12H11NCCH3]-: A Simple and Effective Route to the New BNCT Drug Design

In the present work, a convenient and straightforward approach to the preparation of borylated amidines based on the closo-dodecaborate anion [B₁₂H₁₁NCCH₃NHR]-, R=H, Alk, Ar was developed. This method has two stages. A nitrile derivative of the general form [B₁₂H₁₁NCCH₃]^- was obtained, using a modified technique, in the first stage. On the second stage the resulting molecular system interacted with primary amines to form the target amidine products. This approach is characterised by a simple chemical apparatus, mild conditions and high yields of the final products. The mechanism of the addition of amine to the nitrile derivative of the closo-dodecaborate anion was studied, using quantum-chemical methods. The interaction between NH₃ and [B₁₂H₁₁NCCH₃]^- ammonia was chosen as an example. It was found that the structure of the transition state determines the stereo-selectivity of the process. A study of the biological properties of borylated amidine sodium salts indicated that the substances had low toxicity and could accumulate in cancer cells in significant amounts.

Cascade Transformations of 1-R-Ethynyl-9,10-anthraquinones with Amidines: Expanding Access to Isoaporphinoid Alkaloids

The interaction of acetamidine and phenylamidine with peri-R-ethynyl-9,10-anthraquinones in refluxing n-butanol leads to the formation of cascade transformations products: addition/elimination/cyclization-2-R-7H-dibenzo[de,h]quinolin-7-ones and(or) 2-R-3-aroyl-7H-dibenzo[de,h]quinolin-7-ones. The anti-inflammatory and antitumor properties of the new 2-R-7H-dibenzo[de,h]quinolin-7-ones were investigated in vivo, in vitro, and in silico. The synthesized compounds exhibit high anti-inflammatory activity at dose 20 mg/kg (intraperitoneal injection) in the models of exudative (histamine-induced) and immunogenic (concanavalin A-induced) inflammation. Molecular docking data demonstrate that quinolinones can potentially intercalate into DNA similarly to the antitumor drug doxorubicin.

A Novel Prodrug of a nNOS Inhibitor with Improved Pharmacokinetic Potential

Under different pathological conditions, aberrant induction of neuronal nitric oxide synthase (nNOS) generates overproduction of NO that can cause irreversible cell damage. The aim of this study was to develop an amidoxime prodrug of a potent nNOS inhibitor, the benzhydryl acetamidine. We synthesized the benzhydryl acetamidoxime, which was evaluated in vitro to ascertain the potential NOS inhibitory activity, as well as conducting bioconversion into the parent acetamidine. The prodrug was also profiled for in vitro physicochemical properties, by determining the lipophilicity, passive permeation through the human gastrointestinal tract and across the blood-brain barrier by PAMPA, and chemical, enzymatic, and plasma stability. The obtained data demonstrate that the amidoxime prodrug shows an improved pharmacokinetic profile with respect to the acetamidine nNOS inhibitor, thus suggesting that it could be a promising lead compound to treat all those pathological conditions in which nNOS activity is dysregulated.

Intercepted Retro-Nazarov Reaction: Syntheses of Amidino-Rocaglate Derivatives and Their Biological Evaluation as eIF4A Inhibitors

Rocaglates are a family of natural products isolated from the genus Aglaia which possess a highly substituted cyclopenta[b]benzofuran skeleton and inhibit cap-dependent protein synthesis. Rocaglates are attractive compounds due to their potential for inhibiting tumor cell maintenance in vivo by specifically targeting eukaryotic initiation factor 4A (eIF4A) and interfering with recruitment of ribosomes to mRNA. In this paper, we describe an intercepted retro-Nazarov reaction utilizing intramolecular tosyl migration to generate a reactive oxyallyl cation on the rocaglate skeleton. Trapping of the oxyallyl cation with a diverse range of nucleophiles has been used to generate over 50 novel amidino-rocaglate (ADR) and amino-rocaglate derivatives. Subsequently, these derivatives were evaluated for their ability to inhibit cap-dependent protein synthesis where they were found to outperform previous lead compounds including the rocaglate hydroxamate CR-1-31-B.

Evaluation of analogues of furan-amidines as inhibitors of NQO2

Inhibitors of the enzyme NQO2 (NRH: quinone oxidoreductase 2) are of potential use in cancer chemotherapy and malaria. We have previously reported that non-symmetrical furan amidines are potent inhibitors of NQO2 and here novel analogues are evaluated. The furan ring has been changed to other heterocycles (imidazole, N-methylimidazole, oxazole, thiophene) and the amidine group has been replaced with imidate, reversed amidine, N-arylamide and amidoxime to probe NQO2 activity, improve solubility and decrease basicity of the lead furan amidine. All compounds were fully characterised spectroscopically and the structure of the unexpected product N-hydroxy-4-(5-methyl-4-phenylfuran-2-yl)benzamidine was established by X-ray crystallography. The analogues were evaluated for inhibition of NQO2, which showed lower activity than the lead furan amidine. The observed structure-activity relationship for the furan-amidine series with NQO2 was rationalized by preliminary molecular docking and binding mode analysis. In addition, the oxazole-amidine analogue inhibited the growth of Plasmodium falciparum with an IC50 value of 0.3 μM.

Development of Phenyl Cyclohexylcarboxamides as a Novel Class of Hsp90 C-terminal Inhibitors

Inhibition of the heat shock protein 90 (Hsp90) C-terminus represents a promising therapeutic strategy for the treatment of cancer. Novobiocin, a coumarin antibiotic, was the first Hsp90 C-terminal inhibitor identified, however, it manifested poor anti-proliferative activity (SKBr3, IC50 ≈700 μm). Subsequent structure-activity relationship (SAR) studies on novobiocin led to development of several analogues that exhibited improved anti-proliferative activity against several cancer cell lines. Recent studies demonstrate that the biphenyl core could be used in lieu of the coumarin ring system, which resulted in more efficacious analogues. In continuation of previous efforts, the work described herein has identified the phenyl cyclohexyl core as a novel scaffold for Hsp90 C-terminal inhibition. Structure-activity relationship (SAR) studies on this scaffold led to the development of compounds that manifest mid-nanomolar activity against SKBr3 and MCF-7 breast cancer cell lines through Hsp90 inhibition.

Arabinoamidine synthesis and its inhibition toward β-glucosidase (sweet almonds) in comparison to a library of galactonoamidines

Aiming at the development of potent inhibitors of β-glucosidases, a small library of galactonoamidines and one arabinoamidine derived in analogy were studied as inhibitors of sweet almond β-glucosidase. The five-membered glycon in arabinoamidine was shown to interact with the proton donor in the active site of the retaining enzyme, but not with the nucleophile. By contrast, the corresponding galactonoamidine with a six-membered glycon and identical aglycon interacts with both hydrolysis-promoting amino acids in the active site and inhibits the enzymatic hydrolysis of β-glucosides in the low nanomolar concentration range. While both inhibitors are competitive, their inhibition ability is more than 37,000-fold different.

Non-symmetrical furan-amidines as novel leads for the treatment of cancer and malaria

NRH:quinone oxidoreductase 2 enzyme (NQO2) is a potential therapeutic target in cancer and neurodegenerative diseases, with roles in either chemoprevention or chemotherapy. Here we report the design, synthesis and evaluation of non-symmetrical furan-amidines and their analogues as novel selective NQO2 inhibitors with reduced adverse off-target effects, such as binding to DNA. A pathway for the synthesis of the non-symmetrical furan-amidines was established from the corresponding 1,4-diketones. The synthesized non-symmetrical furan-amidines and their analogues showed potent NQO2 inhibition activity with nano-molar IC50 values. The most active compounds were non-symmetrical furan-amidines with meta- and para-nitro substitution on the aromatic ring, with IC50 values of 15 nM. In contrast to the symmetric furan-amidines, which showed potent intercalation in the minor grooves of DNA, the synthesized non-symmetrical furan-amidines showed no affinity towards DNA, as demonstrated by DNA melting temperature experiments. In addition, Plasmodium parasites, which possess their own quinone oxidoreductase PfNDH2, were inhibited by the non-symmetrical furan-amidines, the most active possessing a para-fluoro substituent (IC50 9.6 nM). The high NQO2 inhibition activity and nanomolar antimalarial effect of some of these analogues suggest the lead compounds are worthy of further development and optimization as potential drugs for novel anti-cancer and antimalarial strategies.

Supramolecular polymers as surface coatings: rapid fabrication of healable superhydrophobic and slippery surfaces

Supramolecular polymerization for non-wetting surface coatings is described. The self-assembly of low-molecular-weight gelators (LMWGs) with perfluorinated side chains can be utilized to rapidly construct superhydrophobic, as well as liquid-infused slippery surfaces within minutes. The lubricated slippery surface exhibits impressive repellency to biological li-quids, such as human serum and blood, and very fast self-healing.

Potent and selective double-headed thiophene-2-carboximidamide inhibitors of neuronal nitric oxide synthase for the treatment of melanoma

Selective inhibitors of neuronal nitric oxide synthase (nNOS) are regarded as valuable and powerful agents with therapeutic potential for the treatment of chronic neurodegenerative pathologies and human melanoma. Here, we describe a novel hybrid strategy that combines the pharmacokinetically promising thiophene-2-carboximidamide fragment and structural features of our previously reported potent and selective aminopyridine inhibitors. Two inhibitors, 13 and 14, show low nanomolar inhibitory potency (Ki = 5 nM for nNOS) and good isoform selectivities (nNOS over eNOS [440- and 540-fold, respectively] and over iNOS [260- and 340-fold, respectively]). The crystal structures of these nNOS-inhibitor complexes reveal a new hot spot that explains the selectivity of 14 and why converting the secondary to tertiary amine leads to enhanced selectivity. More importantly, these compounds are the first highly potent and selective nNOS inhibitory agents that exhibit excellent in vitro efficacy in melanoma cell lines.

Fluorescent substituted amidines of benzanthrone: synthesis, spectroscopy and quantum chemical calculations

Several new substituted amidine derivatives of benzanthrone were synthesized by a condensation reaction from 3-aminobenzo[de]anthracen-7-one and appropriate aromatic and aliphatic amides. The obtained derivatives have a bright yellow or orange fluorescence in organic solvents and in solid state. The novel benzanthrone derivatives were characterized by TLC analysis, (1)H NMR, IR, MS, UV/vis, and fluorescence spectroscopy. The solvent effect on photophysical behaviors of these dyes was investigated, and the results showed that the Stoke's shift increased, whereas quantum yield decreased with the growth of the solvent polarity. The structure of some dyes was confirmed by the X-ray single crystal structure analysis. AM1, ZINDO/S and ab initio calculations using Gaussian software were carried out to estimate the electron system of structures. The calculations show planar configurations for the aromatic core of these compounds and two possible orientations of amidine substituents. The calculation results correlate well with red-shifted absorption and emission spectra of compounds.

The induction of microRNA-16 in colon cancer cells by protein arginine deiminase inhibition causes a p53-dependent cell cycle arrest

Protein Arginine Deiminases (PADs) catalyze the post-translational conversion of peptidyl-Arginine to peptidyl-Citrulline in a calcium-dependent, irreversible reaction. Evidence is emerging that PADs play a role in carcinogenesis. To determine the cancer-associated functional implications of PADs, we designed a small molecule PAD inhibitor (called Chor-amidine or Cl-amidine), and tested the impact of this drug on the cell cycle. Data derived from experiments in colon cancer cells indicate that Cl-amidine causes a G1 arrest, and that this was p53-dependent. In a separate set of experiments, we found that Cl-amidine caused a significant increase in microRNA-16 (miRNA-16), and that this increase was also p53-dependent. Because miRNA-16 is a putative tumor suppressor miRNA, and others have found that miRNA-16 suppresses proliferation, we hypothesized that the p53-dependent G1 arrest associated with PAD inhibition was, in turn, dependent on miRNA-16 expression. Results are consistent with this hypothesis. As well, we found the G1 arrest is at least in part due to the ability of Cl-amidine-mediated expression of miRNA-16 to suppress its' G1-associated targets: cyclins D1, D2, D3, E1, and cdk6. Our study sheds light into the mechanisms by which PAD inhibition can protect against or treat colon cancer.

Analogs of N'-hydroxy-N-(4H,5H-naphtho[1,2-d]thiazol-2-yl)methanimidamide inhibit Mycobacterium tuberculosis methionine aminopeptidases

Our previous target validation studies established that inhibition of methionine aminopeptidases (MtMetAP, type 1a and 1c) from Mycobacterium tuberculosis (Mtb) is an effective approach to suppress Mtb growth in culture. A novel class of MtMetAP1c inhibitors comprising of N'-hydroxy-N-(4H,5H-naphtho[1,2-d]thiazol-2-yl)methanimidamide (4c) was uncovered through a high-throughput screen (HTS). A systematic structure-activity relationship study (SAR) yielded variants of the hit, 4b, 4h, and 4k, bearing modified A- and B-rings as potent inhibitors of both MtMetAPs. Except methanimidamide 4h that showed a moderate Mtb inhibition, a desirable minimum inhibitory concentration (MIC) was not obtained with the current set of MtMetAP inhibitors. However, the SAR data generated thus far may prove valuable for further tuning of this class of inhibitors as effective anti-tuberculosis agents.

Synthesis, spectroscopic characterization and X-ray structure of [1,2a]benzimidazol-2-yl amidine

[1,2a]Benzimidazol-2-yl amidine was synthesized by adding cyclopentanamine to iminoester in ethanol. The structure of amidine 1 was characterized by IR, 1H NMR, 1H-1H NOESY, 13C NMR, DEPT, XHCOR spectra, thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry thermograms (DSC), elementary analysis as well as by X-ray diffraction. The single crystals suitable for X-ray measurement were obtained by recrystallization at room temperature. The amidine group of a model was found to have Z configuration in the crystal. This compound crystallizes in a P2(1)/n monoclinic unit cell with parameters a=12.679(2) Å, b=8.468(3) Å, c=13.108(2) Å, β=96.538(2)°, V=1398.2 Å3 and Z=4.

N-allyl-N-sulfonyl ynamides as synthetic precursors to amidines and vinylogous amidines. An unexpected N-to-C 1,3-sulfonyl shift in nitrile synthesis

A detailed study of amidine synthesis from N-allyl-N-sulfonyl ynamides is described here. Mechanistically, this is a fascinating reaction consisting of diverging pathways that could lead to deallylation or allyl transfer depending upon the oxidation state of palladium catalysts, the nucleophilicity of amines, and the nature of the ligands. It essentially constitutes a Pd(0)-catalyzed aza-Claisen rearrangement of N-allyl ynamides, which can also be accomplished thermally. An observation of N-to-C 1,3-sulfonyl shift was made when examining these aza-Claisen rearrangements thermally. This represents a useful approach to nitrile synthesis. While attempts to render this 1,3-sulfonyl shift stereoselective failed, we uncovered another set of tandem sigmatropic rearrangements, leading to vinyl imidate formation. Collectively, this work showcases the rich array of chemistry one can discover using these ynamides.

Gold-catalyzed nitrene transfer to activated alkynes: formation of α,β-unsaturated amidines

A gold-catalyzed intermolecular nitrene transfer to alkynes was developed for the first time, revealing a new mode of nitrene transfer and providing a novel access to versatile α-imino metal carbenes. Various mild nitrene-transfer reagents were examined, and iminopyridium ylides especially those based on 3,5-dichloropyridine proved be highly effective. With activated alkynes such as N-alkynyloxazolidinones as substrates, α,β-unsaturated amidines were formed in mostly good yields.

Synthesis, X-ray crystallography characterization, vibrational spectroscopic, molecular electrostatic potential maps, thermodynamic properties studies of N,N'-di(p-thiazole)formamidine

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of N,N'-di(p-thiazole)formamidine (DpTF). DpTF has been synthesized and characterized by elemental analysis, FT-IR, FT-Raman, 1H NMR, 13C NMR spectroscopy and X-ray single crystal diffraction. The FT-IR and FT-Raman spectra of DpTF were recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods using 6-31G(d) basis set. The FT-IR and FT-Raman spectra of DpTF was calculated at the HF/B3LYP/6-31G(d) level and were interpreted in terms of potential energy distribution (PED) analysis. The scaled theoretical wavenumber showed very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of DpTF was reported. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between Cp,m°, Sm°, Hm° and temperatures. Furthermore, molecular electrostatic potential maps (MESP) and total dipole moment properties of the compound have been calculated.

X-ray crystallography characterization, vibrational spectroscopy, NMR spectra and quantum chemical DFT/HF study of N,N'-di(2-methoxyphenyl)formamidine

The title compound, N,N'-di(2-methoxyphenyl)formamidine (DMPF) was synthesized and characterized by FT-IR, FT-Raman, (1)H NMR, (13)C NMR spectroscopy and X-ray single crystal diffraction. The results show that the compound crystallizes in an orthorhombic system, with space group of Pbca and eight molecules in the unit cell. The unit cell parameters are: a=11.1118 (7)A, b=14.9878 (9)A and c=16.2851 (10)A. The molecular geometry, the normal mode frequencies and corresponding vibrational assignments of DMPF at the ground state were performed by HF and B3LYP methods with 6-311+G(d,p) basis set. It was observed that the bond lengths and angles in the molecule, obtained by X-ray at the level of theory, were in good agreement with those of the experiment. A detailed interpretation of the infrared and Raman spectra of DMPF was reported. The (13)C NMR and (1)H NMR of DMPF have been calculated using HF and B3LYP methods with 6-311+G(d,p) basis set. Comparison between experimental and theoretical results showed that B3LYP/6-311+G(d,p) method is able to provide more satisfactory results for predicting IR, Raman, (1)H NMR and (13)C NMR properties.

A chloroacetamidine-based inactivator of protein arginine methyltransferase 1: design, synthesis, and in vitro and in vivo evaluation

Protein arginine methyltransferases (PRMTs) catalyze the post-translational methylation of arginine residues. PRMT1 is the predominant mammalian isozyme, and is responsible for generating the majority of the asymmetrically dimethylated arginine found in vivo . The dysregulation of this enzyme has been implicated in heart disease and cancer; thus, its inhibition would be useful in the treatment of these diseases. Herein, we describe the most potent PRMT1 inhibitor described to date. This compound, denoted C21, is a chloroacetamidine-containing peptide that is able to irreversibly bind and inactivate the enzyme selectively. We have also shown that the coactivator activity of PRMT1 is selectively inhibited by the compound in cellulo .

Synthesis and antiprotozoal activity of cationic 1,4-diphenyl-1H-1,2,3-triazoles

Novel dicationic triazoles 1-60 were synthesized by the Pinner method from the corresponding dinitriles, prepared via the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The type and the placement of cationic moieties as well as the nature of aromatic substituents influenced in vitro antiprotozoal activities of compounds 1-60 against Trypanosoma brucei rhodesiense, Plasmodium falciparum, and Leishmania donovani and their cytotoxicity for mammalian cells. Eight congeners displayed antitrypanosomal IC(50) values below 10 nM. Thirty-nine dications were more potent against P. falciparum than pentamidine (IC(50) = 58 nM), and eight analogues were more active than artemisinin (IC(50) = 6 nM). Diimidazoline 60 exhibited antiplasmodial IC(50) value of 0.6 nM. Seven congeners administered at 4 x 5 mg/kg by the intraperitoneal route cured at least three out of four animals in the acute mouse model of African trypanosomiasis. At 4 x 1 mg/kg, diamidine 46 displayed better antitrypanosomal efficacy than melarsoprol, curing all infected mice.

[Design, synthesis and 5-HT/NE dual reuptake inhibitory activity of aromatic heterocyclic arylamidine derivatives]

Based on the pharmacophore information and the analysis of structure-activity relationship of SSRIs and SNRIs, a series of substituted aromatic heterocyclic arylamidine derivatives were designed and synthesized in order to search for lead compounds with dual activity. All of them were new compounds, and their structures were confirmed by 1H NMR and HRMS. Preliminary in vitro pharmacological tests showed that all target compounds exhibited 5-HT reuptake inhibitory activity and some compounds exhibited NE reuptake inhibitory activity. These aromatic heterocyclic arylamidine designed can be further optimized for finding more potent 5-HT/NE dual reuptake inhibitors and antidepressant candidates as well.

Synthesis of amidines using N-allyl ynamides. A palladium-catalyzed allyl transfer through an ynamido-pi-allyl complex

A de novo transformation of N-allyl-N-sulfonyl ynamides to amidines is described featuring a palladium-catalyzed N-to-C allyl transfer via ynamido-palladium-pi-allyl complexes.

Amidine Analogues of Melphalan: Synthesis, Cytotoxic Activity, and DNA Binding Properties

Design, synthesis, and cytotoxic activity of amidine derivatives of melphalan are described and structure-activity relationships are discussed. Evaluation of the cytotoxicity of these compounds employing a MTT assay and inhibition of [(3)H]thymidine incorporation into DNA in both MDA-MB-231 and MCF-7 human breast cancer cells demonstrated that these compounds were more active than melphalan. Data from the ethidium displacement assay showed that these compounds were able to bind in the minor groove-binding mode in AT sequences of DNA. The cytotoxic properties of the amidine analogues of melphalan towards cultured human breast cancer cells correlate with topoisomerase II inhibitory properties but not with DNA-binding properties.

Synthesis of amino acid-derived cyclic acyl amidines for use in beta-strand peptidomimetics

The acyl amidine represented by the 4,5-dihydro-2(3H)-pyrazinone ring system 2 is isosteric to the vinylogous amide of the 1,2-dihydro-3(6H)-pyridinone 1, but its assembly from separate amine and amide components enables ready incorporation of an amino acid side chain with correct regio- and stereochemistry. beta-Strand peptidomimetics incorporating amino acid analogues based on 2 have recently been shown to be potent, protease-resistant ligands to a PDZ protein-interaction domain. Two routes to the protected dipeptide analogue 3 are described.

Unsymmetrical NiII–Imidoylamidine Complexes Derived from a Novel Oxime-Mediated Single-Pot Reaction of Nitriles

The neutral bisimidoylamidine (or 1,3,5-triazapentadiene) Ni(II) complexes [Ni{HN=C(R)N=C(C(6)H(4)CO)N}(2)] {R=Me, Et, nPr, iPr, (CH(2))(3)Cl}, bearing an iminoisoindolinone moiety, have been generated by a novel 2-propanone oxime-mediated single-pot reaction of phthalonitrile and nickel(II) acetate in solution of the corresponding alkylnitrile (RCN). Single-crystal X-ray diffraction analyses indicate a square-planar geometry of the imidoylamidine core. The synthesised compounds represent rare specimens of genuine unsymmetrical imidoylamidine complexes as well as their first examples generated from nitriles in a single-pot reaction.

Molecular design and synthesis of artificial double helices

This account describes novel artificial double helices recently developed by our group. We have designed and synthesized the double helices consisting of two complementary, m-terphenyl-based strands that are intertwined through chiral amidinium-carboxylate salt bridges. Due to the chiral substituents on the amidine groups, the double helices adopted an excess one-handed helical conformation in solution as well as in the solid state. By extending the modular strategy, we have synthesized double helices bearing Pt(II) linkers, which underwent the double helix-to-double helix transformations through the chemical reactions of the Pt(II) complex moieties. In addition, artificial double-stranded metallosupramolecular helical polymers were constructed by combining the salt bridges and metal coordination. In contrast to the design-oriented double helices based on salt bridges, we have serendipitously developed a spiroborate-based double helicate bearing oligophenol strands. The optical resolution of the helicate was successfully attained by a diastereomeric salt formation. We have also unexpectedly found that oligoresorcinols consisting of a very simple repeating unit self-assemble into double helices with the aid of aromatic interactions in water. Furthermore, a bias in the twist sense of the double helices can be achieved by incorporating chiral substituents at both ends of the strands.

Synthesis and antimalarial activity of new 1,12-bis(N,N'-acetamidinyl)dodecane derivatives

Amidoxime and O-substituted derivatives of the bis-alkylamidine 1,12-bis(N,N'-acetamidinyl)dodecane were synthesized and evaluated as in vitro and in vivo antimalarial prodrugs. The bis-O-methylsulfonylamidoxime 8 and the bis-oxadiazolone 9 derivatives show relatively potent antimalarial activity after oral administration.

Identification of isothiazole-4-carboxamidines derivatives as a novel class of allosteric MEK1 inhibitors

The development of potent, orally bioavailable, and selective series of 5-amino-3-hydroxy-N(1-hydroxypropane-2-yl)isothiazole-4-carboxamidine inhibitors of MEK1 and MEK-2 kinase is described. Optimization of the carboxamidine and the phenoxyaniline group led to the identification of 55 which gave good potency as in vitro MEK1 inhibitors, and good oral exposure in rat.

Identification of novel, selective and potent Chk2 inhibitors

A series of isothiazole carboxamidine compounds were synthesized and discovered as novel and selective inhibitors for Chk2. They are not active against the related Chk1 kinase. The structure-activity relationship studies were performed on the scaffold, and enzymatic kinetic analysis showed they are simple ATP competitive inhibitors with K(i) values as low as 11 nM for Chk2. Computer modeling studies were employed to comprehend the mechanism of action and SAR of these compounds.

Secondary amides of sulfonylated 3-amidinophenylalanine. New potent and selective inhibitors of matriptase

Matriptase is an epithelium-derived type II transmembrane serine protease and has been implicated in the activation of substrates such as pro-HGF/SF and pro-uPA, which are likely involved in tumor progression and metastasis. Through screening, we have identified bis-basic secondary amides of sulfonylated 3-amidinophenylalanine as matriptase inhibitors. X-ray analyses of analogues 8 and 31 in complex with matriptase revealed that these inhibitors occupy, in addition to part of the previously described S4-binding site, the cleft formed by the molecular surface and the unique 60 loop of matriptase. Therefore, optimization of the inhibitors included the incorporation of appropriate sulfonyl substituents that could improve binding of these inhibitors into both characteristic matriptase subsites. The most potent derivatives inhibit matriptase highly selective with K(i) values below 5 nM. Molecular modeling revealed that their improved affinity results from interaction with the S4 site of matriptase. Analogues 8 and 59 were studied in an orthotopic xenograft mouse model of prostate cancer. Compared to control, both inhibitors reduced tumor growth, as well as tumor dissemination.

Synthesis, anti-inflammatory and analgesic activity evaluation of some amidine and hydrazone derivatives

A number of amidine derivatives (3a-i) were synthesized by condensation of cyanopyridine and cyanopyrazine with sulfonylhydrazides in the presence of sodium methoxide. 2-Acetylpyridine and 4-acetylpyridine were condensed with sulfonylhydrazides by microwave irradiation in solid phase to give corresponding hydrazones (5a-d). Indole-3-carboxaldehyde was condensed with sulfonylhydrazides by refluxing in acetic acid to give corresponding condensation product (5e and f). All the compounds, that is, 3a-i and 5a-f were purified by crystallization or by column chromatography. Structures of all the synthesized compounds are supported by correct IR, (1)H NMR, mass spectral and analytical data. Anti-inflammatory activity evaluation was carried out using carrageenin-induced paw oedema assay and compounds 3e,f and 5e exhibited good anti-inflammatory activity, that is 52%, 37% and 38% at 50 mg/kg po, respectively. Analgesic activity evaluation was carried out using acetic acid writhing assay and compounds 3a,c,e and 5f showed good analgesic activity, that is, 50%, 50%, 50% and 60% at 50 mg/kg po, respectively.

Towards NR2B receptor selective imaging agents for PET-synthesis and evaluation of N-[11C]-(2-methoxy)benzyl (E)-styrene-, 2-naphthyl- and 4-trifluoromethoxyphenylamidine

Three potent and selective 11C-labelled NR2B antagonists have been synthesized and evaluated as PET ligands. The brain uptake of the compounds in mice varied substantially and was dominated by metabolism. One compound was found to have favourable uptake and retention in the brain, as well as a binding pattern consistent with the expression of the target receptor as measured by in vitro autoradiography. However, the metabolism of the compounds tested was too rapid to allow for in vivo imaging.

An Efficient Direct Amination of Cyclic Amides and Cyclic Ureas

[reaction: see text] An efficient one-step amination of cyclic amides and ureas has been developed. Treatment of cyclic amides and cyclic ureas with BOP in the presence of DBU in various solvents led to the formation of cyclic amidines and cyclic guanidines in good to excellent yields. Concise syntheses of biologically intriguing kinetin and potent kinase inhibitor olomoucin were thus achieved in just one and two steps, respectively.

Novel amidine analogue of melphalan as a specific multifunctional inhibitor of growth and metabolism of human breast cancer cells

A novel amidine analogue of melphalan (AB4) was compared to its parent drug, melphalan in respect to cytotoxicity, DNA and collagen biosynthesis in MDA-MB-231 and MCF-7 human breast cancer cells. It was found that AB4 was more active inhibitor of DNA and collagen synthesis as well more cytotoxic agent than melphalan. The topoisomerase I/II inhibition assay indicated that AB4 is a potent catalytic inhibitor of topoisomerase II. Data from the ethidium displacement assay showed that AB4 intercalated into the minor-groove at AT sequences of DNA. The greater potency of AB4 to suppress collagen synthesis was found to be accompanied by a stronger inhibition of prolidase activity and expression compared to melphalan. The phenomenon was related to the inhibition of beta(1)-integrin and IGF-I receptor mediated signaling caused by AB4. The expression of beta(1)-integrin receptor, as well as Sos-1 and phosphorylated MAPK, ERK(1) and ERK(2) but not FAK, Shc, and Grb-2 was significantly decreased in cells incubated for 24h with 20 microM AB4 compared to the control, not treated cells, whereas in the same conditions melphalan did not evoke any changes in expression of all these signaling proteins, as shown by Western immunoblot analysis. These results indicate the amidine analogue of melphalan, AB4 represent multifunctional inhibitor of breast cancer cells growth and metabolism.

A fluoroacetamidine-based inactivator of protein arginine deiminase 4: design, synthesis, and in vitro and in vivo evaluation

Protein arginine deiminase 4 (PAD4) is a calcium-dependent transcriptional corepressor that has been implicated in the onset and progression of rheumatoid arthritis. Herein we describe the synthesis and in vitro evaluation of a fluoroacetamidine-containing compound, N-alpha-benzoyl-N5-(2-fluoro-1-iminoethyl)-l-ornithine amide, 1, hereafter referred to as F-amidine, that is the most potent PAD4 inhibitor ever described. Additional studies described herein indicate that F-amidine can also inhibit PAD4 activity in vivo. The bioavailability of this compound suggests that F-amidine will be a powerful chemical probe of PAD4 function that can be used to dissect the roles of this enzyme in both rheumatoid arthritis and transcriptional control. The fact that inhibition is of an irreversible nature suggests that, with appropriate functionalization, F-amidine analogues will be robust activity-based protein-profiling and proteomic capture reagents.

Efficient Microwave Access to Polysubstituted Amidines from Imidoylbenzotriazoles

Microwave reactions of primary and secondary amines with imidoylbenzotriazoles 6a-w gave diversely substituted amidines 7a-Aa in 76-94% yields. Convenient preparations of a variety of amides 5a-Ab (87-96%) and imidoylbenzotriazoles 6a-w (56-95%) have also been developed using microwave irradiation under mild conditions and short reaction times. These results demonstrate further the advantages of microwave synthesis and introduce a new application of imidoylbenzotriazoles in the preparation of polysubstituted amidines.

Radiosynthesis of (E)-N-(2-[11C]methoxybenzyl)-3-phenyl-acrylamidine, a novel subnanomolar NR2B subtype-selective NMDA receptor antagonist

Recently, a novel series of amidines has been described, exhibiting high NR2B-subtype selective N-methyl-D-aspartate (NMDA) antagonist activity with nanomolar or subnanomolar affinity. Within the styrylamidine subclass, (E)-N-(2-methoxybenzyl)-3-phenyl-acrylamidine (1), displayed the highest affinity (Ki=0.7 nM versus [(3)H]ifenprodil) and was considered an appropriate candidate for isotopic labelling with carbon-11 (T(1/2): 20.38 min) at its methoxy group for imaging of NMDA receptors with PET. Derivative 1 has been labelled from the corresponding nor-analogue using [(11)C]methyl triflate and the following experimental conditions : (1) trapping at -10 degrees C of [(11)C]methyl triflate in 300 microL of acetone containing 0.6-0.8 mg of precursor 5 (2.4-3.2 micromol) and 5 microL of a 3M solution of NaOH in water (about 5 eq.); (2) concentration to dryness of the reaction mixture (at 110 degrees C, using a helium stream for 1-2 min); (3) taking up the residue with 0.5 mL of the HPLC mobile phase and (4) purification using semi-preparative HPLC (SymmetryPrep) C-18, Waters, 300 x 7.8 mm). Typically, starting from a 1.5 Ci (55.5 GBq) [(11)C]CO(2) production batch, 120-240 m Ci (4.44-8.88 GBq) of [(11)C]-1 (20-40% decay-corrected radiochemical yield, n=5) was obtained within a total synthesis time of 25-30 min. Specific radioactivities ranged from 0.8 to 1.2 Ci/micromol (29.6-44.4 GBq/micromol) at the end of radiosynthesis. No attempts were made to further optimise these reactions, as sufficient material was obtained to allow for preliminary pharmacological characterisation.

A novel series of arylsulfonylthiophene-2-carboxamidine inhibitors of the complement component C1s

Inhibiting the classical pathway of complement activation by attenuating the proteolytic activity of the serine protease C1s is a potential strategy for the therapeutic intervention in disease states such as hereditary angioedema, ischemia-reperfusion injury, and acute transplant rejection. A series of arylsulfonylthiophene-2-carboxamidine inhibitors of C1s were synthesized and evaluated for C1s inhibitory activity. The most potent compound had a Ki of 10nM and >1000-fold selectivity over uPA, tPA, FX(a), thrombin, and plasmin.

Racemic N-aryl bis(amidines) and bis(amidinates): on the trail of enantioselective organolanthanide catalysts

A series of racemic N-aryl-substituted trans-1,2-diaminocyclohexyl (t-1,2-DACH)-linked bis(amidines) were synthesised and their solution behaviour, and solid-state structures were investigated. The amidine functionalities within these compounds were extremely sterically hindered, with ortho-aryl substitution found to hinder N-Ar bond rotation. The results of these studies were used to rationalise the lack of reactivity of these compounds with [Y{N(SiMe(3))(2)}(3)]. Dilithiation of the t-1,2-DACH linked bis(amidines) did, however, proceed easily and the solution behaviour and solid-state structures of the resulting THF-solvated lithium amidinates were investigated. All the compounds showed similar structures in the solid-state, while NMR experiments indicated that the solid-state structures were likely to be maintained in solution. Attempted metathesis reactions with YCl(3) did not, however, yield the desired yttrium chloride complexes.

Microwave-assisted cyclic amidine synthesis using TiCl4

Microwave-assisted treatment of various heterocyclic amides (benzodiazepinone, phthalazone) with TiCl(4) in the presence of primary or secondary amines provides the corresponding amidines. In addition to the interest of the microwaves for this reaction, our study highlights the higher reactivity of the cyclic acetamide moiety compared to the cyclic benzamide moiety towards this TiCl(4)-mediated reaction.

Effect of Polyamine Homologation on the Transport and Biological Properties of Heterocyclic Amidines

Five sets of heterocyclic derivatives of various sizes and complexities coupled by an amidine function to putrescine, spermidine, or spermine were prepared. They were essentially tested to determine the influence of the polyamine chain on their cellular transport. To comment on affinity and on selective transport via the polyamine transport system (PTS), K(i) values for polyamine uptake were determined in L1210 cells, and the cytotoxicity and accumulation of the conjugates were determined in CHO and polyamine transport-deficient mutant CHO-MG cells, as well as in L1210 and alpha-difluoromethylornithine- (DFMO-) treated L1210 cells. Unlike spermine, putrescine and spermidine were clearly identified as selective motifs that enable cellular entry via the PTS. However, this property was clearly limited by the size of substituents: these polyamines were able to ferry a dihydroquinoline system via the PTS but did not impart any selectivity to bulkier substituents.

Synthesis and potent antimicrobial activity of some novel N-(alkyl)-2-phenyl-1H-benzimidazole-5-carboxamidines

A series of 22 novel 1,2-disubstituted-1H-benzimidazole-N-alkylated-5-carboxamidine derivatives were synthesized and evaluated for in vitro antibacterial activity against S. aureus and methicillin resistant S. aureus (MRSA), E. coli, E.faecalis and for antifungal activity against C. albicans. Compound 59 [1-(2,4-dichlorobenzyl)-N-(2-diethylaminoethyl)-1H-benzimidazole-5-carboxamidine], with a 3,4-dichlorophenyl group at the C-2 position, displayed the greatest activity (MIC = 3.12 μg/mL against both some bacteria and the fungus C. albicans).

A ratiometric fluorescence sensor with broad dynamic range based on two pH-sensitive fluorophores

This paper describes a novel ratiometric fluorescence sensor for pH measurement. Two pH-sensitive fluorophores, N-allyl-4-(4'-methyl-piperazinyl)-1,8-naphthalimide (AMPN) and meso-5,10,15,20-tetra-(4-allyloxyphenyl)porphyrin (TAPP), which served as referencing indicators for each other, were co-polymerized with acrylamide, hydroxyethyl methacrylate and triethylene glycol dimethacrylate on the silanized glass surface. The proposed sensor is based on the pH-dependent fluorescence intensities of the two fluorophores in different pH ranges. The sensor covers a broad dynamic range of pH 1.5-9.0. It exhibits satisfactory analytical performance in terms of selectivity, reproducibility and stability. The successful fabrication of the proposed sensor provides an alternative concept to utilizing two or more fluorophores for the development of ratiometric sensors covering a broad range of pH.

Synthesis and potent antibacterial activity against MRSA of some novel 1,2-disubstituted-1H-benzimidazole-N-alkylated-5-carboxamidines

A series of 28 novel 1,2-disubstituted-1H-benzimidazole-N-alkylated-5-carboxamidine derivatives were synthesized and evaluated for in vitro antibacterial activities against Staphylococcus aureus and methicillin resistant S. aureus (MRSA) by the tube dilution method. The results showed that compounds 45-46 and 55-57, having 3,4-dichloro substituted phenyl at the position C-2, of N-bulky alkyl substituted benzimidazolecarboxamidines exhibited the greatest activity with MIC values of 1.56-0.39 microg/ml.

Solid-phase synthesis of naphthylamidines as factor VIIa/tissue factor inhibitors

Reductive amination followed by acylation of polymer-linked formyl aryl amidines generate combinatorial libraries of aryl amidines 8-13. Potent small molecule naphthylamidine inhibitors 12 (Ki<100 nM) of FVIIa/TF have been discovered and their activity against other serine proteases in the coagulation cascade is reported.

Inhibitors of Trypanosoma cruzi trypanothione reductase revealed by virtual screening and parallel synthesis

In an approach to discover new inhibitors of trypanothione reductase from Trypanosoma cruzi, the causative agent of Chagas' disease, a virtual high-throughput screening was performed. Two structurally new types of inhibitors emerged, the antimicrobial chlorhexidine {1,1'-hexamethylenebis[5-(4-chlorophenyl)biguanide]}, a linear competitive inhibitor (K(i) = 2 +/- 1 microM), and a piperidine derivative acting as mixed inhibitor (K(i) = 6.2 +/- 2 microM and K(i)' = 8.5 +/- 2 microM). Neither compound interferes with human glutathione reductase. Based on chlorhexidine, different series of compounds were synthesized and studied as inhibitors of T. cruzi trypanothione reductase. Most efficient derivatives were three bis(amidines) showing mixed type inhibition with K(i,slope) and K(i,int) values of 2-5 microM and 16-47 microM, respectively. Although these compounds did not exert an improved inhibitory potency compared to chlorhexidine, the change from competitive to mixed-type inhibition is advantageous, since substrate accumulation does not overcome inhibition. Remarkably, all three derivatives carried two copies of an identical 2-methoxy-4-methyl-1-(phenylmethoxy)benzene substituent.

Novel Cyano- and N-Isopropylamidino-Substituted Derivatives of Benzo[b]thiophene-2-carboxanilides and Benzo[b]thieno[2,3-c]quinolones: Synthesis, Photochemical Synthesis, Crystal Structure Determination, and Antitumor Evaluation. 2

Derivatives of 3-chlorobenzo[b]thiophene-2-carboxanilides and their "cyclic" analogues benzo[b]thieno[2,3-c]quinolones were synthesized. Spectroscopic study of the interactions of some representatives of "cyclic" derivatives and their "acyclic" precursors with ds-DNA/RNA supported strong intercalative binding of the former and weak nonintercalative binding of the latter group of compounds. All tested compounds showed a certain antiproliferative effect on a series of human tumor cells and on a normal cell line. Among the compounds, those with one amidino-substituent have shown the best effect. The most active benzo[b]thieno[2,3-c]quinolones induced apparent S and G2/M arrests of the cell cycle, which resulted in apoptosis. These results strongly suggest that the compounds may act as topoisimerase "poisons", which is in good agreement with their intercalative mode of binding to ds-DNA/RNA, in contrast to the studied "acyclic"group of derivatives. 6a and 6d showed the best selectivity by inhibiting the growth of tumor cells but not of normal fibroblasts.

Highly Efficient One-Pot Synthesis of N-Sulfonylamidines by Cu-Catalyzed Three-Component Coupling of Sulfonyl Azide, Alkyne, and Amine

A highly efficient, mild, practical, and catalytic multicomponent reaction for the synthesis of N-sulfonylamidines has been developed. This reaction has an extremely wide scope with regard to all three coupling components of alkyne, sulfonyl azide, and amine. Two plausible mechanistic pathways involving ketenimine or triazole intermediate are tentatively presented for the copper-catalyzed three-component coupling reactions.