Heterocyclic derivatives of naphthalene-1,8-dicarboxylic anhydride. Part I. Nitro-7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-ones

Condensation of o-phenylenediamine with 2-, 3- and 4-nitronaphthalene-1,8-dicarboxylic anhydrides gives, in each case, an isomer mixture. Separation of the mixtures into the six isomeric mononitro-7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-ones is described and the isomers characterised in respect of previously reported data on some isomers; ir and mass spectrum data are reported, the latter showing fragmentation ions which may be used in characterising dyes based on this chromophore. Other new derivatives of 7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-one are also described.     

Isolation and Crystallographic Characterization of Two,Nonisolated Pentagon Endohedral Fullerenes: Ho3N@C2(22010)-C78 and Tb3N@C2(22010)-C78

Purified samples of Ho₃N@C₂(22010)-C₇₈ and Tb₃N@C₂(22010)-C₇₈ have been isolated by two distinct processes from the rich array of fullerenes and endohedral fullerenes present in carbon soot from graphite rods doped with Ho₂O₃ or Tb₄O₇. Crystallographic analysis of the endohedral fullerenes as cocrystals with Ni(OEP) (in which OEP is the dianion of octaethylporphyrin) shows that both molecules contain the chiral C₂(22010)-C₇₈ cage. This cage does not obey the isolated pentagon rule (IPR) but has two sites where two pentagons share a common C−C bond. These pentalene units bind two of the metal ions, whereas the third metal resides near a hexagon of the cage. Inside the cages, the Ho₃N or Tb₃N unit is planar. Ho₃N@C₂(22010)-C₇₈ and Tb₃N@C₂(22010)-C₇₈ use the same cage previously found for Gd₃N@C₂(22010)-C₇₈ rather than the IPR-obeying cage found in Sc₃N@D_3h-C₇₈.     

Addition Reactions of Benzenesulfinic Acid with Glycals and 1,2-Dibromosugars

The addition of benzenesulfinic acid to glycals was investigated under various conditions, and optimized yields of the glycosyl phenylsulfone products were obtained in the presence of tin tetrachloride as a catalyst. Double bond shift (Ferrier rearrangement) occurred in all cases except amicetal, which lacks a substituent at the allylic carbon. Glycosylation of benzenesulfinic acid with 1,2-dibromides was carried out using silver triflate as the promoter, and gave sulfinate esters as products by reaction at oxygen rather than at sulfur. The sulfinate esters were obtained as mixtures of stereoisomers at the stereogenic sulfur atom. Trapping of the sulfinates with carboxylate nucleophiles was observed during attempted oxidation with MCPBA.     

Unusual open chain quinolinyl peroxol and its alcohol counterpart obtained through a modified Skraup–Doebner–Von Miller quinoline synthesis: theoretical studies and complete 1H‐ and 13C‐NMR assignments

Because of their extreme instability, it is generally difficult to synthesize and fully characterize open chain peroxides, also known as peroxols. In our attempt to investigate the mechanism of the Skraup–Doebner–Von Miller quinoline synthesis, we were able to obtain an unusual open chain peroxy‐quinoline, namely, 4‐(8‐ethoxy‐2,3‐dihydro‐1H‐cyclopenta[c]quinolin‐4‐yl)butane‐1‐peroxol (1), and its alcohol counterpart, namely 4‐(8‐ethoxy‐2,3‐dihydro‐1H‐cyclopenta[c]quinolin‐4‐yl)butan‐1‐ol (2) obtained as a side product during the same reaction. Although structurally similar, these two compounds appeared to display some very distinct physical and spectroscopic characteristics. This work reports detailed NMR studies and full ¹H and ¹³ C NMR assignments for these two compounds. These assignments are based upon the analysis of the NMR spectra of these compounds including ¹H, ¹³ C, COSY, gHSQC and gHMBC. The effect of the peroxide functional group on the chemical shift of neighboring carbons and protons was also investigated by comparing the NMR data of these two compounds. Furthermore, the effects of potential hydrogen bondings in 1, 2, and possible 1–1 dimer, 2–2 dimer and in prototypical model systems, as well as the stability of these compounds, were investigated computationally. The computed dissociation energies and NMR data support the interpretation of the experimental data. Copyright © 2012 John Wiley & Sons, Ltd.     

Radical–radical coupling of polystyrene chains using AGET ATRC

Activators generated by electron transfer (AGET) was integrated into atom transfer radical coupling (ATRC) systems to drastically reduce the amount of copper catalyst required to achieve dimerization of monohalogenated polystyrene (PStX) precursors. PStCl or PStBr, prepared by ATRP, were activated and coupled in ATRC systems with varying equivalents of the reducing agent tin(II) ethyl hexanoate (Sn(EH)₂) with ligand‐bound copper(I) and/or copper(II) present. Effective coupling was only observed in PStBr systems, with total copper content in the reaction mixture able to be reduced into the range of 10–25% of what is typically reported in traditional ATRC reactions of PSt while maintaining coupling yields of >50%. Additional reducing agents, glucose and ascorbic acid, were also studied and were found to be even more effective in some AGET ATRC reactions compared with Sn(EH)₂. Best results were achieved with ascorbic acid as the reducing agent (>80% coupled product) with total copper content 25% of what was used for a traditional ATRC. Using an activators regenerated by electron transfer ATRP–AGET ATRC sequence resulted in an overall reduction of total copper down to 0.1–0.25% for the overall reaction sequence (compared with a traditional ATRP–ATRC sequence). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A Short and Efficient Synthesis of the [3]Triangulene Ring System

Triangulenes are of current interest for potential applications in molecular electronics. We describe here a three step synthesis of the 4,8,12‐trihydro[3]triangulenium cation by cascade cyclization of a tetra‐benzyl alcohol precursor in triflic acid solution. This stable carbocation is easily observed by NMR and optical spectroscopy and is highly fluorescent. Quenching of the cation into basic solutions or by hydride transfer from triethylsilane provides access to stable dihydro and tetrahydro[3]triangulenes. These neutral species interconvert with cations in a complex series of proton and hydride transfers. This route provides several important [3]triangulene precursors. Preliminary experiments designed to generate [3]triangulene in the solution phase provide evidence for its formation and rapid oligomerization.     

Combined Short-Term Glucose Starvation and Chemotherapy in 3D Colorectal Cancer Cell Culture Decreases 14-3-3 Family Protein Expression and Phenotypic Response to Therapy

Short-term glucose starvation prior to chemotherapy has the potential to preferentially weaken cancer cells, making them more likely to succumb to treatment, while protecting normal cells. In this study, we used 3D cell cultures of colorectal cancer and assessed the effects of short-term glucose starvation and chemotherapy compared to treatment of either individually. We evaluated both phenotypic changes and protein expression levels. Our findings indicate that the combined treatment results in more significant phenotypic responses, including decreased cell viability and clonogenicity. These phenotypic responses can be explained by the decreased expression of LDHA and 14-3-3 family proteins, which were found only in the combined treatment groups. This study indicates that short-term glucose starvation has the potential to increase the efficacy of current cancer treatment regimes.

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Heterocyclic derivalives of naphthalene-1,8-dicar boxylie anhydride. Part III. Benzo[k,l] thioxanthene-3,4-dicarboximides

Condensation of 4-bromo- ( 4 ) and 4-nilro-l,8-naphthalimides ( 5 ) with 2-aminobenzenethiol gave 4-(2-aminoulicnylthio)-1,8-naphthalimides ( 7 ). Cyclisalion of 7 by the: Pschorr reaction afforded benzo[k,l] thioxanthene-3,4-dicarboximides ( 8 ), also obtained by reaction ol amities with benzo[k,l] thioxanthene-3,4-dicarboxylie anhydride ( 11 ).     

Lens epithelial cell response to polymer stiffness and polymer chemistry

Posterior capsule opacification (PCO) is the most common complication of cataract surgery, and intraocular lens (IOL) implantation is the standard of care for cataract patients. Induction of postoperative epithelial-mesenchymal transition (EMT) in residual lens epithelial cells (LEC) is the main mechanism by which PCO forms. Previous studies have shown that IOLs made with different materials have varying incidence of PCO. The aim of this paper was to study the interactions between human (h)LEC and polymer substrates. Polymers and copolymers of 2-hydroxyethyl methacrylate (HEMA) and 3-methacryloxypropyl tris(trimethylsiloxy)silane (TRIS) were synthesized and evaluated due to the clinical use of these materials as ocular biomaterials and implants. The chemical properties of the polymer surfaces were evaluated by contact angle, and polymer stiffness and roughness were measured using atomic force microscopy. In vitro studies showed the effect of polymer mechanical properties on the behavior of hLECs. Stiffer polymers increased α-smooth muscle actin expression and induced cell elongation. Hydrophobic and rough polymer surfaces increased cell attachment. These results demonstrate that attachment of hLECs on different surfaces is affected by surface properties in vitro, and evaluating these properties may be useful for investigating prevention of PCO.     

A versatile approach for the syntheses of poly(ester amide)s with pendant functional groups

Poly(ester amide)s (PEAs) are emerging as promising materials for a wide range of biomedical applications due to their potential for both hydrolytic and enzymatic degradation, as well as the ease with which their properties can be tuned by the choice of monomers. The incorporation of pendant functional handles along the PEA backbone has the potential to further expand their applications by allowing the charge and hydrophilicity of the polymers to be altered, and facilitating the conjugation of active molecules such as drugs, targeting groups, and cell signaling molecules. Described here is a simple and versatile strategy based on orthogonal protecting groups, by which L ‐lysine and L‐ aspartic acid can be incorporated into several families of PEAs based on monomers including the diacids succinic and terephthalic acid, the diols 1,4‐butanediol and 1,8‐octanediol, and the amino acids L‐ alanine and L‐ phenylalanine. All polymers were thoroughly characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. It was demonstrated that the side chain protecting groups could be readily removed, allowing the pendant amines or carboxylic acids to be functionalized. In particular, the carboxylic acid groups on a polymer containing L‐ aspartic acid units were converted to N‐hydroxysuccinimidyl esters, providing a useful template for further derivatization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3757–3772, 2009