Novel Pyridine-Containing Sultones: Structure-Activity Relationship and Biological Evaluation as Selective AChE Inhibitors for the Treatment of Alzheimer's disease.

Novel pyridine-containing sultones were synthesized and evaluated for their cholinesterase (ChE) inhibitory activity. Most of compounds showed selective acetylcholinesterase (AChE) inhibitory activity. The structure-activity relationship (SAR) showed: (i) the fused pyridine-containing sultones increase AChE inhibition, series B>series A; (ii) for series A, the effect of the 4-substituent on AChE activity, p->m- or o-; (iii) for series B, a halophenyl group increase activity. Compound B4 (4-(4-chlorophenyl)-2,2-dioxide-3,4,5,6-tetrahydro-1,2-oxathiino[5,6-h]quinoline) was identified as a selective AChE inhibitor (IC50 =8.93 µM), and molecular docking studies revealed a good fit into TcAChE via hydrogen interactions between the δ-pyridylsultone scaffold with Asp72, Ser122, Phe288, Phe290 and Trp84. Compound B4 showed reversible and non-competitive (Ki =7.67 µM) AChE inhibition, nontoxicity and neuroprotective activity. In vivo studies confirmed that compound B4 could ameliorate the cognitive performance of scopolamine-treated C57BL/6 J mice, suggesting a significant benefit of AChE inhibition for a disease-modifying treatment of AD.

Fluorescence Spectroscopy Analysis of the Bacteria-Mineral Interface: Adsorption of Lipopolysaccharides to Silica and Alumina.

We present here a quantification of the sorption process and molecular conformation involved in the attachment of bacterial cell wall lipopolysaccharides (LPSs), extracted from Escherichia coli, to silica (SiO2) and alumina (Al2O3) particles. We propose that interfacial forces govern the physicochemical interactions of the bacterial cell wall with minerals in the natural environment, and the molecular conformation of LPS cell wall components depends on both the local charge at the point of binding and hydrogen bonding potential. This has an effect on bacterial adaptation to the host environment through adhesion, growth, function, and ability to form biofilms. Photophysical techniques were used to investigate adsorption of fluorescently labeled LPS onto mineral surfaces as model systems for bacterial attachment. Adsorption of macromolecules in dilute solutions was studied as a function of pH and ionic strength in the presence of alumina and silica via fluorescence, potentiometric, and mass spectrometry techniques. The effect of silica and alumina particles on bacterial growth as a function of pH was also investigated using spectrophotometry. The alumina and silica particles were used to mimic active sites on the surface of clay and soil particles, which serve as a point of attachment of bacteria in natural systems. It was found that LPS had a high adsorption affinity for Al2O3 while adsorbing weakly to SiO2 surfaces. Strong adsorption was observed at low pH for both minerals and varied with both pH and mineral concentration, likely in part due to conformational rearrangement of the LPS macromolecules. Bacterial growth was also enhanced in the presence of the particles at low pH values. This demonstrates that at a molecular level, bacterial cell wall components are able to adapt their conformation, depending on the solution pH, in order to maximize attachment to substrates and guarantee community survival.

Discovery of δ-sultone-fused pyrazoles for treating Alzheimer's disease: Design, synthesis, biological evaluation and SAR studies.

A class of novel δ-sulfonolactone-fused pyrazole scaffold was prepared via sulfur (VI) fluoride exchange (SuFEx) chemistry using aryl sulfonyl fluorides and pyrazolones. Enzyme screening revealed their cholinesterase inhibitory activity, among them, compounds 4a, 5a and 5d were identified as highly selective submicromolar BuChE inhibitors (IC50 = 0.20, 0.46 and 0.42 µM, respectively), which exhibited nontoxicity, lipophilicity and remarkable neuroprotective activity. Kinetic studies showed that BuChE inhibition of compounds 5a and 5d was reversible, mixed-type and non-competitive inhibition against BuChE (Ki = 145 nM and 60 nM, respectively). Compound 5d can be accommodated into hBuChE via π-S interaction and hydrophobic interactions. The title compounds are potentially symptomatic treatment in progressive Alzheimer's disease.

Polymeric fluorescent heparin as one-step FRET substrate of human heparanase.

Heparanase, an endo-ß-D-glucuronidase, cleaves cell surface and extracellular matrix heparan sulfate (HS) chains and plays important roles in cellular growth and metastasis. Heparanase assays reported to-date are labor intensive, complex and/or expensive. A simpler assay is critically needed to understand the myriad roles of heparanase. We reasoned that fluorescent heparin could serve as an effective probe of heparanase levels. Following synthesis and screening, a heparin preparation labeled with DABCYL and EDANS was identified, which exhibited a characteristic increase in signal following cleavage by human heparanase. This work describes the synthesis of this heparin substrate, its kinetic and spectrofluorometric properties, optimization of the heparanase assay, use of the assay in inhibitor screening, and elucidation of the state of heparanase in different cell lines. Our FRET-based assay is much simpler and more robust than all assays reported in the literature as well as a commercially available kit.

Synthesis of Trifluoromethylated Sultones from Alkenols Using a Copper Photoredox Catalyst.

A photo-redox-catalyzed procedure for the one-step formation of sultones from α,ω-alkenols and trifluoromethylsulfonyl chloride is described. Using [Cu(dap)2]Cl (1 mol %), a wide range of substrates can be cleanly converted to the target compounds, while commonly employed photoelectron transfer catalysts such as [Ru(bpy)3]Cl2 or fac-Ir(ppy)3 fail in this transformation. The obtained fluorinated sultones are attractive as potential electrolyte additives or as structural motifs in drug synthesis, with the latter being demonstrated with the synthesis of a trifluoroethyl-substituted analogue of a benzoxathiin that has high anti-arrhythmic activity.

Modular Synthesis of Novel Macrocycles Bearing α,ß-Unsaturated Chemotypes through a Series of One-Pot, Sequential Protocols.

A series of one-pot, sequential protocols was developed for the synthesis of novel macrocycles bearing α,ß-unsaturated chemotypes. The method highlights a phosphate tether-mediated approach to establish asymmetry, and consecutive one-pot, sequential processes to access the macrocycles with minimal purification procedures. This library amenable strategy provided diverse macrocycles containing α,ß-unsaturated carbon-, sulfur-, or phosphorus-based warheads.

Modular, One-Pot, Sequential Aziridine Ring Opening-S(N)Ar Strategy to 7-, 10-, and 11-Membered Benzo-Fused Sultams.

The generation of common and stereochemically rich medium-sized benzo-fused sultams via complementary pairing of heretofore-unknown (o-fluoroaryl)sulfonyl aziridine building blocks with an array of amino alcohols/amines in a modular one-pot, sequential protocol using an aziridine ring opening and intramolecular nucleophilic aromatic substitution is reported. The strategy employs a variety of amino alcohols/amines and proceeds with 6 + 4/6 + 5 and 6 + 1 cycloetherification pathways in a highly chemo- and regioselective fashion to obtain skeletally and structurally diverse, polycyclic, 10- to 11- and 7-membered benzo-fused sultams for broad-scale screening.

Thermodynamics of binding of a sulfonamide inhibitor to metal-mutated carbonic anhydrase as studied by affinity capillary electrophoresis.

By affinity capillary electrophoresis (ACE), the thermodynamic binding constants of a sulfonamide (SA) inhibitor to bovine carbonic anhydrase II (CA) and metal mutated variants (M-CAs) were evaluated. 1-(4-Aminosulfonylphenylazo)-2-naphthol-6,8-disulfonate was used as the SA in the electrophoretic buffer for ACE. The Scatchard analysis of the dependence of the electrophoretic mobility of native CA on the SA concentration provided the binding constant to be Kb=(2.29±0.05)×10(6) M(-1) (at pH8.4, 25°C). On the other hand, apoCA showed far smaller value [Kb=(3.76±0.14)×10(2) M(-1)], suggesting that the coordination of SA to the Zn(II) center controlled the binding thermodynamics. The ACE of M-CAs showed the same behaviors as native CA but with different Kb values. For example, Co-CA adopting the same tetrahedral coordination geometry as native CA exhibited the largest Kb value [(2.55±0.05)×10(6) M(-1)] among the M-CAs. In contrast, Mn- and Ni-CA, which adopted the octahedral coordination geometry, had Kb values that were about two orders of magnitude lower. Because the hydrophobic cavity of CA around the active center pre-organized the orientation of SA, thereby fixing the ligating NH(-) moiety to the apex of the tetrahedron supported by three basal His3 of CA, metals such as Zn and Co at the center of M-CA gave the most stable CA-SA complex. However, pre-organization was not favored for octahedral geometry. Thus, pre-organization of SA was the key to facilitating the tetrahedral coordination geometry of the Zn(II) active center of CA.

Experimental and Computational Studies of the Diastereoselective Alkylations of 3-Substituted γ-Sultams.

We report that chiral 3-substituted γ-sultam α-carbanions undergo diastereoselective alkylation reactions with alkyl halides to predominantly produce trans-3,5-disubstituted γ-sultam products. Quantum mechanical calculations provided a stereoelectronic rationale for the observed diastereoselectivity.

Synthesis of benzofused five-ring sultams via Rh-catalyzed C-H olefination directed by an N-Ac-substituted sulfonamide group.

A Rh-catalyzed N-Ac-sulfonamide group directed C-H olefination-cyclization to afford benzofused five-ring sultam is described with high yield and a wide range of substrate scope. The N-acetyl group is a key for this transformation implying that N-H acidity is the major influence. The acetyl group is removed under mild conditions in excellent yield to provide NH-free sultam that can be transformed into various benzofused five-ring sultam analogues via acylation, nucleophilic substitution, and Mitsunobu alkylation.

Palladium-catalyzed intramolecular oxidative coupling involving double C(sp(2))-H bonds for the synthesis of annulated biaryl sultams.

The palladium-catalyzed intramolecular oxidative coupling described herein involves a double C(sp(2))-H bond functionalization in sulfonanilides, providing a workable access to biaryl sultams annulated into a six-membered ring that are otherwise difficult to obtain by literature methods. The other synthetic applications of this protocol including the synthesis of biaryl sultams containing a seven-membered ring and analogous sultones are also presented.

Rh(III)-catalyzed synthesis of sultones through C-H activation directed by a sulfonic acid group.

A new rhodium-catalyzed synthesis of sultones via the oxidative coupling of sulfonic acids with internal alkynes is described. The reaction proceeds via aryl C-H activation assisted by a sulfonic acid group.

Novel carbazole inhibits phospho-STAT3 through induction of protein-tyrosine phosphatase PTPN6.

The aberrant activation of STAT3 occurs in many human cancers and promotes tumor progression. Phosphorylation of a tyrosine at amino acid Y705 is essential for the function of STAT3. Synthesized carbazole derived with fluorophore compound 12 was discovered to target STAT3 phosphorylation. Compound 12 was found to inhibit STAT3-mediated transcription as well as to reduce IL-6 induced STAT3 phosphorylation in cancer cell lines expressing both elevated and low levels of phospho-STAT3 (Y705). Compound 12 potently induced apoptosis in a broad number of TNBC cancer cell lines in vitro and was effective at inhibiting the in vivo growth of human TNBC xenograft tumors (SUM149) without any observed toxicity. Compound 12 also effectively inhibited the growth of human lung tumor xenografts (A549) harboring aberrantly active STAT3. In vitro and in vivo studies showed that the inhibitory effects of 12 on phospho-STAT3 were through up-regulation of the protein-tyrosine phosphatase PTPN6. Our present studies strongly support the continued preclinical evaluation of compound 12 as a potential chemotherapeutic agent for TNBC and cancers with constitutive STAT3 signaling.

Synthesis, characterization and in vivo evaluation of [(62)Zn]-benzo-δ-sultam complex as a possible pet imaging agent.

OBJECTIVE: The development of a new tracer based on the cyclic sulfonamides (sultams) was investigated. METHODS: 3-(Methoxy-phenyl-methyl)-1,6-dimethyl-1H benzo[c][1,2] thiazine 2,2-dioxide (benzo-δ-sultam) was synthesized and characterized by elemental analysis, FT-IR spectroscopy and single crystal X-ray structure determination. The prepared cyclic sulfonamide was labeled with non-commercial (62)Zn radioisotope for fast in vivo targeting and Coincidence imaging purposes (radiochemical purity 97 % ITLC, 96 % HPLC, specific activity 20-23 GBq/mmol). In vivo biodistribution of the final complex was investigated in Sprague Dawley(®) rats bearing fibro sarcoma tumor after 2, 4 and 8 h post injection and compared with free Zn(+2) cation. RESULTS: Using instant paper chromatography method, the physicochemical properties of labeled compounds were found sufficiently stable in organic phases, e.g. a human serum, to be reliably used in bioapplications. CONCLUSIONS: The complex exhibited a rapid as well as high tumor uptake (tumor to blood ratio 4.38 and tumor to muscle ratio 9.63) resulting in an efficient tumor targeting agent.

A N-(2-aminophenyl)-5-(dimethylamino)-1-naphthalenesulfonic amide (Ds-DAB) based fluorescent chemosensor for peroxynitrite.

A dansyl derivative (Ds-DAB) was prepared and used as a fluorescent probe for peroxynitrite (ONOO(-)) detection. The results showed that the addition of peroxynitrite to the aqueous solution of Ds-DAB would result in obvious fluorescence enhancement. This probe is highly specific for peroxynitrite in aqueous solution, avoiding interference from other reactive oxygen species (ROS) and nitrogen species (RNS). The advantages of high selectivity, fast reaction rate, and peroxynitrite bioimaging render Ds-DAB suitable for peroxynitrite detection.

Biomedical applications and chemical nature of three dyes first synthesized by Raphael Meldola: isamine blue, Meldola's blue and naphthol green B.

Brief accounts are given of the chemical nature, and past and current biomedical applications of three dyes first synthesized by Raphael Meldola: isamine blue, Meldola's blue and naphthol green B.

Synthesis and reactivity of a bis-sultone cross-linker for peptide conjugation and [18F]-radiolabelling via unusual "double click" approach.

A novel homobifunctional cross-linker based on a bis-sultone benzenic scaffold was synthesised. The potential utility of this bioconjugation reagent was demonstrated through the preparation of an original prosthetic group suitable for the [(18)F]-labelling of peptides. The labelling strategy is based on the nucleophilic fluorination via the ring-opening of a first sultone moiety followed by the nucleophilic ring-opening of the second remanent sultone by a reactive amine of the biopolymer. Beyond the one-step radiolabelling of the peptide, the second main advantage of this strategy is the release of free sulfonic acid moieties making the separation of the targeted [(18)F]-tagged sulfonated compound from its non-sulfonated precursor easier and thus faster. This first report of the successful use of a bis-sultone moiety as a versatile bioconjugatable group was demonstrated through a comprehensive reactivity study involving various nucleophiles, especially those commonly found in biopolymers. An illustrative example, highlighting the potential of this unusual and promising "double click" conjugation approach, was devoted to the radiolabelling of a biological relevant peptide.

Isolation of a sultone as an unusual acetolysis product.

Acetolysis of methyl 5,6-di-O-acetyl-2,3-O-isopropylidene-ß-L-gulofuranoside has yielded a sultone, 4-(1,2,5,6-tetra-O-acetyl-ß-L-gulofuranos-3-yl)-6-methyl-1,2-oxathiin 2,2-dioxide (2) whose structure was determined by X-ray diffraction. (1)H and (13)C NMR spectral properties of 2 are presented together with a rationale for its formation. Preparation and properties of the related α-d-mannofuranos-3-yl compound 4 are described.

Effective and specific inhibition of the CD40-CD154 costimulatory interaction by a naphthalenesulphonic acid derivative.

Costimulatory interactions are important regulators of T-cell activation and, hence, promising therapeutic targets in autoimmune diseases as well as in transplant recipients. Following our recent identification of the first small-molecule inhibitors of the CD40-CD154 costimulatory protein-protein interaction (J Mol Med 87, 2009, 1133), we continued our search within the chemical space of organic dyes, and we now report the identification of the naphthalenesulphonic acid derivative mordant brown 1 as a more active, more effective, and more specific inhibitor. Flow cytometry experiments confirmed its ability to concentration-dependently inhibit the CD154(CD40L)-induced cellular responses in human THP-1 cells at concentrations well below cytotoxic levels. Binding experiments showed that it not only inhibits the CD40-CD154 interaction with sub-micromolar activity, but it also has considerably more than 100-fold selectivity toward this interaction even when compared to other members of the tumor necrosis factor superfamily pairs such as TNF-R1-TNF-α, BAFF-R(CD268)-BAFF(CD257/BLys), OX40(CD134)-OX40L(CD252), RANK(CD265)-RANKL(CD254/TRANCE), or 4-1BB(CD137)-4-1BBL. There is now sufficient structure-activity relationship information to serve as the basis of a drug discovery initiative targeting this important costimulatory interaction.

Delta-sultone formation through Rh-catalyzed C-H insertion.

Rhodium-catalyzed reactions of sulfonate ester derivatives are biased strongly toward 1,6-insertion and thus offer a general method for assembling delta-sultones. Two protocols for staging this cyclization reaction are described, which capitalize on the unique ability of either diazo or iodonium ylide intermediates to form Rh-carbene species. The value of these heterocycles for fine chemicals synthesis is demonstrated in both reductive and oxidative reactions that make possible excision of the -SO3- moiety.