4-Substituted (benzo[b]thiophene-2-carbonyl)guanidines as novel Na+/H+ exchanger isoform-1 (NHE-1) inhibitors

A series of 4-substituted (benzo[b]thiophene-2-carbonyl)guanidines was synthesized and evaluated for the NHE-1 inhibitory activity and cardioprotective efficacy both in vitro and in vivo. Several analogs exhibited a strong inhibition on NHE-1, and which was generally well correlated with their cardioprotective efficacy. Especially the 4-nitro 20 and cyano 50 compounds excellently improved the cardiac function and reduced infarct size against ischemia/reperfusion injury.

(5-Arylfuran-2-ylcarbonyl)guanidines as Cardioprotectives through the Inhibition of Na+/H+ Exchanger Isoform-1

A series of (5-arylfuran-2-ylcarbonyl)guanidines was synthesized and evaluated for the NHE-1 inhibitory activity and cardiprotective efficacy against ischemia-reperfusion injury. Starting with (5-phenylfuran-2-ylcarbonyl)guanidine 47 with a moderate inhibitory effect on NHE-1, the compounds with various substituents at the phenyl ring were investigated with the aim to optimize the potency. In this study, the 2,5-disubstituted compounds appeared to have better activities than the other analogues, and the 2-methoxy-5-chlorophenyl compound 85 was found as a potent inhibitor of NHE-1 (IC(50) = 0.081 microM). Furthermore, 85 showed a marked reduction of infarct size in the rat myocardial infarction model in vivo and significant improvement of cardiac contractile function in the isolated rat heart ischemia model in vitro.

Enantioselective total synthesis of (-)-dehydrobatzelladine C. [structure: see text]

The oxidation of two tethered Biginelli adducts was examined as a potential key step in total syntheses of highly oxidized batzelladine and crambescidin alkaloids. Although angular hydroxyl substitution could not be introduced, dehydrogenation was readily accomplished. This latter conversion is a key step in the first total synthesis of dehydrobatzelladine C. [structure: see text]

DNG cytidine: synthesis and binding properties of octameric guanidinium-linked deoxycytidine oligomer

The synthesis of guanidinium-linked cytidyl oligomer (DNG-C(8)), a cationic DNA analog, and the corresponding cytidine monomers is described. The DNG monomer synthesis was streamlined to produce a shorter route to the final monomer than previously reported for thymidine and subsequent solid-phase synthesis produced an octameric cytidyl DNG strand. Because octameric deoxyguanosine would be used as the complementary strand in our studies, it was necessary to investigate guanosine self-association. Singular value decomposition was used to mathematically deconvolve the spectral data and confirm the presence of transitions due to DNA-G(8) self-association. Job plots show the binding stoichiometry of DNG-C(8) with DNA-G(8) to be 1:1. Thermal denaturation studies of the DNG-C(8).DNA-G(8) duplex established a T(m) > or = 90 degrees and a DeltaG degree = -13.3 kcal mol(-1), indicating the DNG-C(8).DNA-G(8) duplex is over 1000 times more stable than that of DNA-C(8).DNA-G(8).

Amino Acid Binding by 2-(Guanidiniocarbonyl)pyridines in Aqueous Solvents: A Comparative Binding Study Correlating Complex Stability with Stereoelectronic Factors

A series of guanidiniocarbonylpyridine receptors has been synthesized, and these compounds bind amino acids (carboxylate forms) in aqueous DMSO with association constants ranging from K = 30 to 460 M(-1) as determined by NMR titration experiments. The differences in the complex stabilities can be correlated with steric and electrostatic effects with the aid of calculated complex structures. For example, the electrostatic repulsion between the pyridine nitrogen lone pair and the bound carboxylate makes anion binding less efficient than with the analogous pyrrole receptors previously introduced by us for carboxylate binding in water. Furthermore, steric interactions between the receptor side chain as in 2 b and the bound substrate also disfavor complexation.

Design, Syntheses, and Transfection Biology of Novel Non-Cholesterol-Based Guanidinylated Cationic Lipids

The design of efficacious cationic transfection lipids with guanidinium headgroups is an actively pursued area of research in nonviral gene delivery. Herein, we report on the design, syntheses, and gene transfection properties of six novel non-cholesterol-based cationic amphiphiles (1-6) with a single guanidinium headgroup in transfecting CHO, COS-1, MCF-7, A549, and HepG2 cells. The in vitro gene transfer efficiencies of lipids 1-6 were evaluated using both the reporter gene and the whole cell histochemical X-gal staining assays. The efficiencies of lipids 1-3, in particular, were found to be about 2- to 4-fold higher than that of commercially available LipofectAmine in transfecting COS-1, CHO, A-549, and MCF-7 cells. However, the relative transfection efficiencies of lipids 1-3 and LipofectAmine were found to be comparable in HepG2 cells. Cholesterol was found to be a more efficacious co-lipid than dioleoyllphosphatidyl ethanolamine (DOPE). In general, lipids 1-3 containing the additional quaternized centers were observed to be more transfection efficient than lipids 4-6 with less positive headgroups. MTT-assay-based cell viability measurements in representative CHO cells revealed high (>75%) cell viabilities of lipids 1-6 across the lipid/DNA charge ratios 0.1:1 to 3:1. Electrophoretic gel patterns observed in DNase I protection experiments support the notion that enhanced degradation of DNA associated with lipoplexes of lipids 4-6 might play some role in diminishing their in vitro gene transfer efficacies. Size and global surface charge measurement by a dynamic laser light scattering instrument equipped with zeta-sizing capacity revealed the nanosizes and surface potentials of both the transfection efficient and the incompetent lipoplexes to be within the range of 200-600 nm and +3.4 to -34 mV, respectively. To summarize, given the feasibility of a wide range of structural manipulations in the headgroup regions of non-cholesterol-based cationic amphiphiles, our present findings are expected to broaden the potential of cationic amphiphiles with guanidinium headgroups for use in nonviral gene therapy.

New Cellulose-Supported Reagent: A Sustainable Approach to Guanidines

[reaction: see text] A new cellulose-supported reagent for the synthesis of guanidine in aqueous medium is reported starting from commercially available functionalized cellulose beads. Primary and secondary amines, anilines, and amino acids were transformed to the corresponding guanidines in high yields and under very mild conditions.

Multiple Coordination Geometries Supported by Methylene-Linked Guanidines

The methylene-linked bicyclic guanidine based on the 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) framework provides a versatile platform able to support trigonal-planar, tetrahedral, and square-planar metal centers.

Deoxynucleic guanidine; synthesis and incorporation of purine nucleosides into positively charged DNG oligonucleotides

The synthesis of purine nucleosides capable of making the guanidinium linkage is described for the first time starting from the corresponding 2'-deoxynucleosides. The positively charged mixed base DNG oligomer containing guanine was synthesized on solid-phase using CPG as support from 3' to 5' direction using the precursor building block nucleosides.

N-[1-Aryl-2-(1-imidazolo)ethyl]-guanidine derivatives as potent inhibitors of the bovine mitochondrial F1F0 ATP hydrolase

A series of substituted guanidine derivatives were prepared and evaluated as potent and selective inhibitors of mitochondrial F(1)F(0) ATP hydrolase. The initial thiourethane derived lead molecules possessed intriguing in vitro pharmacological profiles, though contained moieties considered non-drug-like. Analogue synthesis efforts led to compounds with maintained potency and superior physical properties. Small molecules in this series which potently and selectivity inhibit ATP hydrolase and not ATP synthase may have utility as cardioprotective agents.

Design and synthesis of novel cyanoguanidine ATP-sensitive potassium channel openers for the treatment of overactive bladder

Thiourea derivatives were identified as glyburide-reversible potassium channel openers through high-throughput screening. Based on these findings, a number of novel cyanoguanidines were designed and synthesized, which hyperpolarized human bladder K(ATP) channels. These agents are potent full agonists in relaxing electrically-stimulated pig bladder strips. The synthesis, SAR and biological properties of these agents are discussed.

Phenylguanidines as selective nonpeptide melanocortin-5 receptor antagonists

A series of phenylguanidine analogues represented by 10, 12, and 21 were synthesized and found to have high binding affinities for the human melanocortin-5 receptor. Their binding affinities for three other melanocortin receptor subtypes, MC1, MC3, and MC4, were low. Selected compounds were also tested for their functional activity and exhibited inhibition of alpha-MSH-stimulated cAMP production in cells expressing the human MC5 receptor. Compound 10 had a K(i) value of 2.1 nM in the binding assay and an IC(50) of 72 nM in the functional assay. Some analogues such as 13 from this series possessed weak agonist activity at the human MC4 receptor.

A 1,3-Diaza-Claisen Rearrangement that Affords Guanidines

[reaction: see text] N-Alkyl-N'-tosylthioureas activated by EDCI react with azanorbonenes at room temperature through a 1,3-diaza-Claisen rearrangement, affording highly substituted, bicyclic guanidines in moderate to good yields.

Inhibition of HIV-1 envelope-mediated fusion by synthetic batzelladine analogues

Marine natural products that feature polycyclic guanidine motifs, such as crambescidins and batzelladines, are known to have antiviral activities toward some viruses including HSV and HIV. In this study we evaluated a synthetic library containing 28 batzelladine analogues, the structures of which encompass and surpass variations seen in natural batzelladines, for their ability to inhibit HIV-1 envelope-mediated cell-cell fusion. Clear structure-activity relationships were revealed and indicated that the best inhibitors of fusion were most similar in structure to natural batzelladine F, with IC50 values ranging from 0.8 to 3.0 microM. Proceeding from the earlier finding that some batzelladines block gp120-CD4 binding, modeling studies of inhibitors binding to the CD4 binding site on gp120 were carried out. The lowest energy models suggest a preferred orientation for inhibitor binding that is consistent with the observed structure-activity relationships.

Arylcyanoguanidines as activators of Kir6.2/SUR1K ATP channels and inhibitors of insulin release

Phenylcyanoguanidines substituted with lipophilic electron-withdrawing functional groups, e.g. N-cyano-N'-[3,5-bis-(trifluoromethyl)phenyl]-N' '-(cyclopentyl)guanidine (10) and N-cyano-N'-(3,5-dichlorophenyl)-N' '-(3-methylbutyl)guanidine (12) were synthesized and investigated for their ability to inhibit insulin release from beta cells, to repolarize beta cell membrane potential, and to relax precontracted rat aorta rings. Structural modifications gave compounds, which selectively inhibit insulin release from betaTC6 cells (e.g. compound 10: IC(50) = 5.45 +/- 1.9 microM) and which repolarize betaTC3 beta cells (10: IC(50) = 4.7 +/- 0.5 microM) without relaxation of precontracted aorta rings (10: IC(50) > 300 microM). Inhibition of insulin release from rat islets was observed in the same concentration level as for betaTC6 cells (10: IC(50) = 1.24 +/- 0.1 microM, 12: IC(50) = 3.8 +/- 0.4 microM). Compound 10 (10 microM) inhibits calcium outflow and insulin release from perifused rat pancreatic islets. The mechanisms of action of 10 and 12 were further investigated. The compounds depolarize mitochondrial membrane from smooth muscle cells and beta cell and stimulate glucose utilization and mitochondrial respiration in isolated liver cells. Furthermore, 10 was studied in a patch clamp experiment and was found to activate Kir6.2/SUR1 and inhibit Kir6.2/SUR2B type of K(ATP) channels. These studies indicate that the observed effects of the compounds on beta cells result from activation of K(ATP) channels of the cell membrane in combination with a depolarization of mitochondrial membranes. It also highlights that small structural changes can dramatically shift the efficacy of the cyanoguanidine type of selective activators of Kir6.2/SUR2 potassium channels.

Synthesis and quantitative structure-activity relationship of hydrazones of N-amino-N'-hydroxyguanidine as electron acceptors for xanthine oxidase

A series of new N-hydroxyguanidines were synthesized and tested for electron acceptor activity on bovine milk xanthine oxidase using xanthine as reducing substrate. Manual inspection of the structure-activity data revealed that molecules containing nitro groups ("set A") show a different structure-activity relationship pattern compared to non-nitro compounds ("set B"). Accordingly separate QSAR models were built and validated for the two sets. Substantial differences were found in properties governing acceptor activity for the models, the only common property being sterical access to the imino nitrogen atom of the hydroxyguanidinimines. For set A molecules the presence of a nitro substituent at a certain distance range from the hydroxuguanidino group was most important. In addition, the presence of a nitro group in the ortho position interacting with NH(2) of the hydroxyguanidino group, and the mutual geometry of the phenyl ring, hydroxyguanidine, and imine groups was important for this set. By contrast, for set B molecules the acceptor activity was most influenced by the geometry of methoxy groups and the size and geometry of meta and para substituents of the phenyl ring.

Oxyguanidines. Part 2: Discovery of a novel orally active thrombin inhibitor through structure-based drug design and parallel synthesis

Through structure-based drug design and parallel synthesis, we have discovered a novel series of nonpeptidic phenyl-based thrombin inhibitors using oxyguanidines as guanidine bioisosteres. These compounds have been found to be highly potent, highly selective, and orally bioavailable.

Studies towards the total synthesis of batzelladine A

Application of a diastereoselective three-component coupling to the bicyclic core of the batzelladine alkaloids is described. The synthesis features the elaboration of glutamic acid by use of Eschenmoser sulfide contraction. An earlier approach is also included, which shows some limitations of dithiane chemistry when applied to the particular compounds required for this target.

Synthesis and in vitro antifungal activity of 4-substituted phenylguanidinium salts

A series of 4-substituted phenylguanidinium derivatives was synthesized and its antimicrobial activity was evaluated in vitro against eight potentially pathogenic strains of fungi.

Design and Synthesis of Novel Biologically Active Thrombin Receptor Non-Peptide Mimetics Based on the Pharmacophoric Cluster Phe/Arg/NH2 of the Ser42-Phe-Leu-Leu-Arg46 Motif Sequence: Platelet Aggregation and Relaxant Activities

The identification of the thrombin receptor has promoted the interest for the development of new therapeutic agents capable of selectively inhibiting unwanted biological effects of thrombin on various cell types. In this study we have designed and synthesized two series of new thrombin receptor antagonists based on the thrombin receptor motif sequence S42FLLR46, one possessing two (Phe/Arg) pharmacophoric groups and the other possessing three (Phe/Arg/NH2). N-(6-Guanidohexanoyl)-N'-(phenylacetyl)piperazine (1), N-(phenylacetyl)-4-(6-guanidohexanoylamidomethyl)piperidine (2), and N-(phenylacetyl)-3-(6-guanidohexanoylamido)pyrrolidine (3) (group A) carry the two pharmacophoric side chains of Phe and Arg residues incorporated on three different templates (piperazine, 4-aminomethylpiperidine, and 3-aminopyrrolidine). Compounds with three pharmacophoric groups (group B) were built similarly to group A using the same templates with the addition of an extra methylamino group leading to (S)-N-(6-guanidohexanoyl)-N'-(2-amino-3-phenylpropionyl)piperazine (4), (S)-N-(2-amino-3-phenylpropionyl)-4-(6-guanidohexanoylamidomethyl)piperidine (5), and (S)-N-(2-amino-3-phenylpropionyl)-3-(6-guanidohexanoylamido)pyrrolidine (6). Compounds were able to inhibit thrombin-induced human platelet activation even at low concentrations. In particular, among compounds in group A, compound 3 was found to be the most powerful thrombin receptor activation inhibitor, showing an IC50 of approximately 0.11 mM on platelet aggregation assay. Among compounds in group B, compound 4 was the most powerful to inhibit thrombin-induced platelet aggregation, showing an IC50 of approximately 0.09 mM. All compounds were also found to act as agonists in the rat aorta relaxation assay. Interestingly, the order of potency of these compounds as agonists of the endothelial thrombin receptor was the inverse of the order of potency of the same compounds as antagonists of the platelet thrombin receptor. Such compounds that are causing vasodilation while simultaneously inhibiting platelet aggregation would be very useful in preventing the installation of atherosclerotic lesions and deserve further investigation as potential drugs for treating cardiovascular diseases. The above findings coupled with computational analysis molecular dynamics experiments support also our hypothesis that a cluster of phenyl, guanidino, and amino groups is responsible for thrombin receptor triggering and activation.

Synthesis and structure activity relationship of guanidines as NPY Y5 antagonists

A series of bis-aryl substituted guanidines have been discovered as potent NPY Y5 antagonists. The SAR and in vitro metabolic stability of these compounds are discussed.

Cytotoxic α-Halogenoacrylic Derivatives of Distamycin A and Congeners

The mechanism of action of many antitumor agents involves DNA damage, either by direct binding of the drug to DNA or to DNA-binding proteins. However, most of the DNA-interacting agents have only a limited degree of sequence specificity, which implies that they may hit all the cellular genes. DNA minor groove binders, among which the derivatives of distamycin A play an important role, could provide significant improvement in cancer management, increasing gene specificity, due to high selectivity of interaction with thymine-adenine (TA) rich sequences. We now report and discuss the synthesis, the in vitro and in vivo activities, and some mechanistic features of alpha-halogenoacrylamido derivatives of distamycin A. The final result of this work was the selection of brostallicin 17 (PNU-166196). Brostallicin, presently in phase II clinical trials, shows a broad spectrum of antitumor activity and an apoptotic effect higher than distamycin derivative tallimustine. An important in vitro toxicological feature of brostallicin is the very good ratio between myelotoxicity on human haematopoietic progenitor cells and cytotoxicity on tumor cells, in comparison with clinically tested DNA minor groove binders. A peculiarity of brostallicin is its in vitro reactivity in the DNA alkylation assays only in the presence of glutathione. Moreover brostallicin's antitumor activity, both in in vitro and in vivo tumor models, is higher in the presence of increased levels of glutathione/glutathione-S-tranferases. These findings contribute to the definition of brostallicin as a novel anticancer agent that differs from other minor groove binders and alkylating agents for both the profile of activity and the mechanism of action and to classify the alpha-bromoacrylamido derivatives of distamycin as a new class of cytotoxics. Moreover, due to its interaction with glutathione, brostallicin may have a role for the tailored treatment of tumors characterized by constitutive or therapy-induced overexpression of glutathione/glutathione-S-tranferase levels.

Bisguanidine, Bis(2-aminoimidazoline), and Polyamine Derivatives as Potent and Selective Chemotherapeutic Agents against Trypanosoma brucei rhodesiense. Synthesis and in Vitro Evaluation

The in vitro screening for trypanocidal activity against Trypanosoma brucei rhodesiense of an in-house library of 62 compounds [i.e. alkane, diphenyl, and azaalkane bisguanidines and bis(2-aminoimidazolines)], which were chosen for their structural similarity to the trypanocidal agents synthalin (1,10-decanediguanidine) and 4,4'-diguanidinodiphenylmethane and the polyamine N(1)-(3-amino-propyl)propane-1,3-diamine, respectively, is reported. The original synthetic procedure for the preparation of 21 of these compounds is also reported. Most compounds displayed low micromolar antitrypanosomal activity, with five of them presenting a nanomolar inhibitory action on the parasite: 1,9-nonanediguanidine (1c), 1,12-dodecanediguanidine (1d), 4,4'-bis[1,3-bis(tert-butoxycarbonyl)-2-imidazolidinylimino]diphenylamine (28a), 4,4'-bis(4,5-dihydro-1H-2-imidazolylamino)diphenylamine (28b), and 4,4'-diguanidinodiphenylamine (32b). Those molecules that showed an excellent in vitro activity as well as high selectivity for the parasite [e.g. 1c (IC(50) = 49 nM; SI > 5294), 28b (IC(50) = 69 nM; SI = 3072), 32b (IC(50) = 22 nM; SI = 29.5), 41b (IC(50) = 118 nM; SI = 881)] represent new antitrypanosomal lead compounds.

Solution- and Solid-Phase Syntheses of Guanidine-Bridged, Water-Soluble Linkers for Multivalent Ligand Design

[reaction: see text] Efficient syntheses of guanidine-bridged poly(ethylene glycol) linkers of various lengths in fully protected form are reported for both solution- and solid-phase protocols. The application of such linkers in the construction of water-soluble and high-affinity multivalent ligands against cholera toxin is demonstrated. Synthetic intermediates for multivalent ligands as large as 20 kDa in molecular weight have been assembled using presynthesized linkers. The final ligands are highly water-soluble, thus enabling proper biophysical characterization.