A Modular Approach to Atropisomeric Bisphosphines of Diversified Electronic Density on Phosphorus Atoms.

The series of C2-symmetric biaryl core-based non-racemic bisphosphines possessing substituents of different electronic properties: both EDG and EWG were obtained in a short sequence of good yielding transformations, started from commercial 1,3-dimethyl-2-nitrobenzene. Several different approaches leading to the desirable ligands were practically evaluated. Notably, the synthesis of the entire series of ligands could be performed with the utilization of a single early-stage precursor DIDAB (6,6'-diiodo-2,2',4,4'-tetramethylbiphenyl-3,3'-diamine), which could be easily obtained in enantiomerically pure form. The obtained compounds at concentrations of 50 and 200 µM showed various biological activity against normal human dermal fibroblast, ranging from inactivity through time-dependent action and ending up with high toxicity.

Design, Synthesis and Activity of New N1-Alkyl Tryptophan Functionalized Dendrimeric Peptides against Glioblastoma.

BACKGROUND: Due to resistance to conventional therapy, a blood-brain barrier that results in poor drug delivery, and a high potential for metastasis, glioblastoma (GBM) presents a great medical challenge. Since the repertoire of the possible therapies is very limited, novel therapeutic strategies require new drugs as well as new approaches. The multiple roles played by L-tryptophan (Trp) in tumorigenesis of GBM and the previously found antiproliferative properties of Trp-bearing dendrimers against this malignancy prompted us to design novel polyfunctional peptide-based dendrimers covalently attached to N1-alkyl tryptophan (Trp) residues. Their antiproliferative properties against GBM and normal human astrocytes (NHA) and their antioxidant potential were tested. METHODS: Two groups of amphiphilic peptide dendrimers terminated with N1-butyl and N1-aminopentane tryptophan were designed. The influence of dendrimers on viability of NHA and human GBM cell lines, displaying different genetic backgrounds and tumorigenic potentials, was determined by the MTT test. The influence of compounds on the clonogenic potential of GBM cells was assessed by colony-formation assay. Dendrimers were tested for radical scavenging potency as well as redox capability (DPPH, ABTS, and FRAP models). RESULTS: Several peptide dendrimers functionalized with N1-alkyl-tryptophan at 5 µM concentration exhibited high selectivity towards GBM cells retaining 85-95% viable NHA cells while killing cancer cells. In both the MTT and colony-formation assays, compounds 21 (functionalized with N1-butyl-Trp and (+)8 charged) and 25 (functionalized with N1-aminopentane-Trp and (+)12 charged) showed the most promise for their development into anticancer drugs. According to ABTS, DPPH, and FRAP antioxidant tests, dendrimers functionalized with N1-alkylated Trp expressed higher ROS-scavenging capacity (ABTS and DPPH) than those with unsubstituted Trp. CONCLUSIONS: Peptide dendrimers functionalized with N1-alkyl-tryptophan showed varying toxicity to NHA, while all were toxic to GBM cells. Based on their activity towards inhibition of GBM viability and relatively mild effect on NHA cells the most advantageous were derivatives 21 and 25 with the respective di-dodecyl and dodecyl residue located at the C-terminus. As expected, peptide dendrimers functionalized with N1-alkyl-tryptophan expressed higher scavenging potency against ROS than dendrimers with unsubstituted tryptophan.

Peptide Dendrimers with Non-Symmetric Bola Structure Exert Long Term Effect on Glioblastoma and Neuroblastoma Cell Lines.

BACKGROUND: Glioblastoma (GBM) is the most common malignant tumor of the central nervous system (CNS). Neuroblastoma (NB) is one of the most common cancers of childhood derived from the neural crest cells. The survival rate for patients with GBM and high-risk NB is poor; therefore, novel therapeutic approaches are needed. Increasing evidence suggests a dual role of redox-active compounds in both tumorigenesis and cancer treatment. Therefore, in this study, polyfunctional peptide-based dendrimeric molecules of the bola structure carrying residues with antiproliferative potential on one side and the antioxidant residues on the other side were designed. METHODS: We synthesized non-symmetric bola dendrimers and assessed their radical scavenging potency as well as redox capability. The influence of dendrimers on viability of rat primary cerebellar neurons (CGC) and normal human astrocytes (NHA) was determined by propidium iodide staining and cell counting. Cytotoxicity against human GBM cell lines, T98G and LN229, and NB cell line SH-SY5Y was assessed by cell counting and colony forming assay. RESULTS: Testing of CGC and NHA viability allowed to establish a range of optimal dendrimers structure and concentration for further evaluation of their impact on two human GBM and one human NB cell lines. According to ABTS, DPPH, FRAP, and CUPRAC antioxidant tests, the most toxic for normal cells were dendrimers with high charge and an excess of antioxidant residues (Trp and PABA) on both sides of the bola structure. At 5 µM concentration, most of the tested dendrimers neither reduced rat CGC viability below 50-40%, nor harmed human neurons (NHA). The same dose of compounds 16 or 22, after 30 min treatment decreased the number of SH-SY5Y and LN229 cells, but did not affect the number of T98G cells 48 h post treatment. However, either compound significantly reduced the number of colonies formed by SH-SY5Y, LN229, and T98G cells measured 14 days after treatment. CONCLUSIONS: Peptide dendrimers with non-symmetric bola structure are excellent scaffolds for design of molecules with pro/antioxidant functionality. Design of molecules with an excess of positive charges and antioxidant residues rendered molecules with high neurotoxicity. Single, 30 min exposition of the GBM and NB cell lines to the selected bola dendrimers significantly suppressed their clonogenic potential.

Bioinspired Bola-Type Peptide Dendrimers Inhibit Proliferation and Invasiveness of Glioblastoma Cells in a Manner Dependent on Their Structure and Amphipathic Properties.

(1) Background: Natural peptides supporting the innate immune system studied at the functional and mechanistic level are a rich source of innovative compounds for application in human therapy. Increasing evidence indicates that apart from antimicrobial activity, some of them exhibit selective cytotoxicity towards tumor cells. Their cationic, amphipathic structure enables interactions with the negatively-charged membranes of microbial or malignant cells. It can be modeled in 3D by application of dendrimer chemistry. (2) Methods: Here we presented design principles, synthesis and bioactivity of branched peptides constructed from ornithine (Orn) assembled as proline (Pro)- or histidine (His)-rich dendrons and dendrimers of the bola structure. The impact of the structure and amphipathic properties of dendrons/dendrimers on two glioblastoma cell lines U87 and T98G was studied with the application of proliferation, apoptosis and cell migration assays. Cell morphology/cytoskeleton architecture was visualized by immunofluorescence microscopy. (3) Results: Dimerization of dendrons into bola dendrimers enhanced their bioactivity. Pro- and His-functionalized bola dendrimers displayed cytostatic activity, even though differences in the responsiveness of U87 and T98G cells to these compounds indicate that their bioactivity depends not only on multiple positive charge and amphipathic structure but also on cellular phenotype. (4) Conclusion: Ornithine dendrons/dendrimers represent a group of promising anti-tumor agents and the potential tools to study interrelations between drug bioactivity, its chemical properties and tumor cells' phenotype.

1,2,4-Triazine Sulfonamides: Synthesis by Sulfenamide Intermediates, In Vitro Anticancer Screening, Structural Characterization, and Molecular Docking Study.

In this study, we synthesized novel sulfonamides with a 1,2,4-triazine moiety according to pharmacophore requirements for biological activity. All the synthesized compounds were tested in vitro to verify whether they exhibited anticancer activity against the human breast cancer cell lines MCF-7 and MDA-MB-231. Among them, two most active ones, having IC50 values of 50 and 42 µM, respectively, were found to show higher anticancer activity than chlorambucil used as the reference in the in vitro tests. In addition, two other compounds, which had IC50 values of 78 and 91 µM, respectively, exhibited a similar level of activity as chlorambucil. X-ray analysis carried out for two of the compounds confirmed their synthesis pathway as well as their assumed molecular structures. Furthermore, a conformational analysis was performed, and electronic parameters of molecules were characterized using theoretical calculations at AM1 and DFT level. Moreover, molecular docking revealed the mode of binding of the investigated 1,2,4-triazine sulfonamides with the human estrogen receptor alpha (ERα).

Peptide dendrimers as antifungal agents and carriers for potential antifungal agent-N3 -(4-methoxyfumaroyl)-(S)-2,3-diaminopropanoic acid-synthesis and antimicrobial activity.

A series of peptide dendrimers and their conjugates with antimicrobial agent FMDP (N3 -(4-methoxyfumaroyl)-(S)-2,3-diamino-propanoic acid) were synthesized. The obtained compounds were tested for the antibacterial and antifungal activity. All novel dendrimers displayed much better activity against the tested strains than FMDP itself. Moreover, their conjugates with FMDP also exhibited antimicrobial activity. The most promising molecules were tested against a broad selection of fungal strains. The analysis of their antifungal properties indicates that the examined molecules are efficient growth inhibitors of fluconazole-resistant hospital-acquired strains. Moreover, an application of amphiphilic branched peptides such as FMDP carriers suggests that transport mechanism involves more likely the cell membrane perturbation than the mediation of the specific transport proteins. The activity of obtained compounds strongly depends on the specific structure of the molecule.

Molecular Antioxidant Properties and In Vitro Cell Toxicity of the p-Aminobenzoic Acid (PABA) Functionalized Peptide Dendrimers.

BACKGROUND: Exposure to ozone level and ultraviolet (UV) radiation is one of the major concerns in the context of public health. Numerous studies confirmed that abundant free radicals initiate undesired processes, e.g. carcinogenesis, cells degeneration, etc. Therefore, the design of redox-active molecules with novel structures, containing radical quenchers molecules with novel structures, and understanding their chemistry and biology, might be one of the prospective solutions. Methods: We designed a group of peptide dendrimers carrying multiple copies of p-aminobenzoic acid (PABA) and evaluated their molecular antioxidant properties in 1,1'-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) tests. Cytotoxicity against human melanoma and fibroblast cells as well as against primary cerebral granule cells (CGC) alone and challenged by neurotoxic sodium glutamate and production of reactive oxygen species (ROS) in presence of dendrimers were measured. Results: PABA-terminated dendrimers express enhanced radical and radical cation scavenging properties in relation to PABA alone. In cellular tests, the dendrimers at 100 M fully suppress and between 20⁻100 M reduce proliferation of the human melanoma cell line. In concentration 20 M dendrimers generate small amount of the reactive oxygen species (<25%) but even in their presence human fibroblast and mouse cerebellar granule cells remain intact Moreover, dendrimers at 0.2⁻20 µM concentration (except one) increased the percentage of viable fibroblasts and CGC cells treated with 100 M glutamate. Conclusions: Designed PABA-functionalized peptide dendrimers might be a potential source of new antioxidants with cationic and neutral radicals scavenging potency and/or new compounds with marked selectivity against human melanoma cell or glutamate-stressed CGC neurons. The scavenging level of dendrimers depends strongly on the chemical structure of dendrimer and the presence of other groups that may be prompted into radical form. The present studies found different biological properties for dendrimers constructed from the same chemical fragments but the differing structure of the dendrimer tree provides once again evidence that the structure of dendrimer can have a significant impact on drug⁻target interactions.

Bioinspired Amphiphilic Peptide Dendrimers as Specific and Effective Compounds against Drug Resistant Clinical Isolates of E. coli.

Evolution-derived natural compounds have been inspirational for design of numerous pharmaceuticals, e.g., penicillins and tetracyclines. Herein, we present a bioinspired strategy to design peptide dendrimers for the effective therapy of E. coli infections where the selection of appropriate amino acids and the mode of their assembly are based on the information gained from research on membranolytic natural antimicrobial peptides (AMP's). On the molecular level two opposite effects were explored: the effect of multiple positive charges necessary for membrane disintegration was equilibrated by the anchoring role of tryptophanes. Indeed, a series of Trp-terminated dendrimers exhibited high potency against clinical isolates of antibiotic resistant ESBL E. coli strains, stability in human plasma along with very low hemo- and genotoxicity. Investigation of the underlying antimicrobial mechanism indicated that the dendrimers studied at minimal inhibitory concentration showed weak permeability toward membranes. Solid-state 2D NMR studies revealed their presence on and inside the model membranes. Therefore, their biological properties might be explained by targeting of extra- or intracellular receptors. Our results point to a new approach to design novel branched antimicrobials with high therapeutic index.

Asymmetric ring-opening reaction of meso-epoxides with aromatic amines using homochiral metal-organic frameworks as recyclable heterogeneous catalysts.

An efficient asymmetric ring-opening (ARO) reaction of meso-epoxides with aromatic amines catalysed by a series of homochiral metal-organic frameworks (MOFs) was carried out. Excellent results (up to 95% ee) for the ARO of cyclohexene oxide with several aromatic amines were achieved with a homochiral MOF derived from the ligand (R)-2,2'-dihydroxyl-1,1'-binaphthalene-5,5'-dicarboxylic acid. Furthermore, homochiral MOFs based on (R)-2,2'-dihydroxy-1,1'-binaphthyl-4,4'-di(4-benzoic acid) and (R)-2,2'-diethoxy-1,1'-binaphthyl-4,4'-di(5-isophthalic acid) catalysed ARO reactions of cis-stilbene oxide with 1-naphthylamine in high yield (up to 95%) and excellent enantioselectivity (up to 97%) of the ß-amino alcohol. The MOF catalysts were recoverable and recyclable with retention of their performance.

Novel thiosemicarbazide derivatives with 4-nitrophenyl group as multi-target drugs: α-glucosidase inhibitors with antibacterial and antiproliferative activity.

A series of thiosemicarbazides with 4-nitrophenyl group was obtained in the reaction of carboxylic acid hydrazides with isothiocyanates. All compounds were checked for their antibacterial and antiproliferative activity. Our results have shown that derivatives 6-8 possessed antibacterial activity against S. aureus, S. epidermidis, S. mutans and S. sanguinis, moderate cytotoxicity and good therapeutic safety in vitro. Additionally, compounds 1 and 4 significantly inhibited A549, HepG2 and MCF-7 cell division. Moreover, PASS software indicated that newly obtained compounds are potential α-glucosidase inhibitors. This was confirmed by in vitro studies. To investigate the mode of interaction with the molecular target compounds were docked to glucose binding site of the enzyme and exhibited a similar binding mode as glucose.

Natural Antimicrobial Peptides as Inspiration for Design of a New Generation Antifungal Compounds.

Invasive fungal infections are associated with high mortality rates, despite appropriate antifungal therapy. Limited therapeutic options, resistance development and the high mortality of invasive fungal infections brought about more concern triggering the search for new compounds capable of interfering with fungal viability and virulence. In this context, peptides gained attention as promising candidates for the antimycotics development. Variety of structural and functional characteristics identified for various natural antifungal peptides makes them excellent starting points for design novel drug candidates. Current review provides a brief overview of natural and synthetic antifungal peptides.

Second Generation Amphiphilic Poly-Lysine Dendrons Inhibit Glioblastoma Cell Proliferation without Toxicity for Neurons or Astrocytes.

Glioblastomas are the most common malignant primary brain tumours in adults and one of the most aggressive and difficult-to-treat cancers. No effective treatment exits actually for this tumour and new therapeutic approaches are needed for this disease. One possible innovative approach involves the nanoparticle-mediated specific delivery of drugs and/or genetic material to glioblastoma cells where they can provide therapeutic benefits. In the present work, we have synthesised and characterised several second generation amphiphilic polylysine dendrons to be used as siRNA carriers. We have found that, in addition to their siRNA binding properties, these new compounds inhibit the proliferation of two glioblastoma cell lines while being nontoxic for non-tumoural central nervous system cells like neurons and glia, cell types that share the anatomical space with glioblastoma cells during the course of the disease. The selective toxicity of these nanoparticles to glioblastoma cells, as compared to neurons and glial cells, involves mitochondrial depolarisation and reactive oxygen species production. This selective toxicity, together with the ability to complex and release siRNA, suggests that these new polylysine dendrons might offer a scaffold in the development of future nanoparticles designed to restrict the proliferation of glioblastoma cells.

Design and studies of multiple mechanism of anti-Candida activity of a new potent Trp-rich peptide dendrimers.

PURPOSE: Eight peptide dendrimers were designed as structural mimics of natural cationic amphiphilic peptides with antifungal activity and evaluated for their anti-Candida potential against the wild type strains and mutants. METHODS: Dendrimer 14 containing four Trp residues and dodecyl tail and a slightly smaller dendrimer 9 decorated with four N-methylated Trp that displayed 100 and 99.7% of growth inhibition at 16 µg/mL respectively, were selected for evaluation against the Candida albicans mutants with disabled biosynthesis of aspartic proteases responsible for host tissue colonization and morphogenesis during biofilm formation (sessile model). Flow cytometry method was employed to detect apoptotic cells with membrane alterations (phosphatidylserine translocation), and differentiation of apoptotic from necrotic cells was also performed. Simultaneous staining of cell surface phosphatidylserine with Annexin-V-Fluorescein and necrotic cells with propidium iodide was conducted. RESULTS: 14 at 16 µg/mL caused C. albicans cells to undergo cellular apoptosis but its increasing concentrations induced necrosis. 14 influenced C. albicans biofilm viability as well as hyphal and cell wall morphology. Confocal microscopy and cell wall staining with calcofluor white revealed that in epithelial model the cell surface structure was perturbed at MIC of peptide dendrimer. It appears that tryptophan or 1-methyltryptophan groups displayed at the surface and positive charges hidden in the dendrimer tree along with hydrocarbon tail located at C-terminus are important for the anti-Candida activity since dendrimers containing tryptamine at C-terminus showed only a moderate activity. CONCLUSIONS: Our results suggest that membranolytic dendrimer 14, targeting cellular apoptotic pathway and impairing the cell wall formation in mature biofilm, may be a potential multifunctional antifungal lead compound for the control of C. albicans infections.

T3P-Promoted, Mild, One-Pot Syntheses of Constrained Polycyclic Lactam Dipeptide Analogues via Stereoselective Pictet-Spengler and Meyers Lactamization Reactions.

A new convenient, mild, one-pot procedure is described for the diastereoselective synthesis of constrained 7,5- and 7,6-fused azabicycloalkanes. Using 2-formyl-L-tryptophan and 2-formyl-l-phenylalanine as bielectrophilic building blocks, T3P-mediated Pictet-Spengler and Meyers lactamization reactions were developed to present chiral and polycyclic aminoindolo- and aminobenzazepinone compounds in excellent yields. The conformationally constrained compounds can serve as templates for peptidomimetic research or polyheterocyclic privileged scaffolds.

Synthesis, Structural Studies and Molecular Modelling of a Novel Imidazoline Derivative with Antifungal Activity.

Six novel imidazoline derivatives were synthesized and tested in antifungal assays. One of the compounds, N-cyclohexyl-2-imino-3-(4-nitrophenyl)imidazolidine-1-carboxamide showed moderate activity against several clinical strains of Candida albicans. Its structure was solved by X-ray crystallography and its mode of action was deduced using molecular modelling. It was found to be similar to that of fluconazole. The potential for further optimization including SAR of the compound is briefly discussed.

Synthetic approaches for sulfur derivatives containing 1,2,4-triazine moiety: their activity for in vitro screening towards two human cancer cell lines.

A series of sulfur 1,2,4-triazine derivatives were prepared and evaluated as anticancer compounds for two human breast cancer cell lines (MCF-7, MDA-MB-231) with some of them acting as low micromolar inhibitors. Evaluation of the cytotoxicity using a 3-(4,5-dimethylthiazol-2-yl)-3,5-diphenyltetrazolium bromide (MTT) assay, the inhibition of [(3)H]thymidine incorporation into DNA, and collagen synthesis inhibition demonstrated that these products exhibit cytotoxic effects on these breast cancer cell lines in vitro. The most effective were disulfide and sulfenamide compounds with two valence sulfur atoms. A structure-activity relationship study was performed using X-ray analysis and theoretical calculations at an ab initio density functional theory (DFT) level.

Solvent-dependent strong asymmetric amplification in the catalytic enantioselective Henry reaction using the trans-N,N'-bis-biphenyl-4-ylmethyl-cyclohexane-1,2-diamine-CuCl2 complex.

A strong asymmetric amplification was observed in the enantioselective Henry reaction catalyzed by the (R,R)-trans-N,N'-bis-biphenyl-4-ylmethyl-cyclohexane-1,2-diamine·CuCl2 complex in AcOEt, while no amplification occurred in MeOH.

New approaches to the synthesis of sildenafil analogues and their enzyme inhibitory activity.

In the search for new biologically active chemotypes, several sildenafil analogs were prepared and characterized. The presence of the pyrazolo[4,3-e][1,2,4]triazine core is thought to be of interest for the enzyme inhibitory activity of these compounds. The designed derivatives incorporating the sildenafil scaffold were assayed as carbonic anhydrase inhibitors, and for their cytotoxic activity against MCF-7 and K562 cell lines. The X-ray analysis of one of these model compounds was performed and its crystal structure is described/compared to that of sildenafil.

On the antimicrobial activity of various peptide-based dendrimers of similar architecture.

Antimicrobial drug resistance is a major human health threat. Among the many attempts to tackle this problem, the synthesis of antimicrobial compounds that mimic natural antimicrobial peptides appears as a promising approach. Peptide-based dendrimers can be designed to have higher potency than natural antimicrobial peptides and at the same time they can evade the bacterial defense system. Novel dendrimers with similar chemical structure but varying potency in terms of minimum inhibitory concentration were designed. The dependency between dendrimer structure and antibacterial activity as well as their capacity to attack model cell membranes was studied. The data suggests that supramolecular structure in terms of charge distribution and amphiphilicity, rather than net charge, is the main driver for disruption of cellular membranes and this correlates well with dendrimer hemolytic activity.

Synthesis of fused 3-aminoazepinones via trapping of a new class of cyclic seven-membered allenamides with furan.

Novel tricyclic tetrahydroazepinones were synthesized via an in situ Diels-Alder reaction of furan with cyclic allenamides. These reactive intermediates are the first examples of cyclic seven-membered allenamides and were prepared starting from N-(2-chloroallyl)-2-allylglycine derivatives via ring-closing metathesis followed by dehydrochlorination. The trapping of the intermediate cycloallene with furan occurred endo- and regioselectively and provided a convenient entry into new building blocks for medicinal chemistry. The diastereoselectivity of the cycloaddition was confirmed using quantum chemical computations.