Microwave-Accelerated Selective Acylation of (Hydroxyalkyl)phenols Using Acid Chlorides

Highly selective acylation of the alcoholic hydroxy group can be achieved with (hydroxyalkyl)phenols carrying both alcoholic and phenolic hydroxyls by the use of the most common acylating agents, acid chlorides, under microwave irradiation.     

Regioselective Alkylation of Thiazolylsulfonamides: Direct and Efficient Synthesis of 3‐Alkylthiazolidene Derivatives

Various N‐3‐alkylated thiazolidenesulfonamide derivatives were efficiently prepared by the direct endo‐selective alkylation of thiazolylsulfonamides. The effects of different bases and solvents were investigated, and the NaH–THF combination was found to be the most effective at conferring high yields and endo‐selectivity.     

Synthesis of novel nematic liquid crystals containing 3,3'-dimethyl-2,2'-bipyridyl

Liquid-crystalline 3,3′-dimethyl-2,2′-bipyridyl derivatives with long 4-(alkoxyphenyl)ethynyl (-C≡C-C₆H₄-OR) groups in the 5,5′-positions were synthesized by palladium-catalysed crosscoupling reactions. The compounds exhibit exclusively nematic behaviour; for example, the hexyl derivative showed a nematic phase over the temperature range 145.2–205.0°C. On increasing the length of the terminal chain, the transition temperatures were lowered; for example, the hexadecyl derivative was nematic in the range 117.0–126.8°C.     

Effect of introducing thioether linkages on the molecular organization of chiral twin liquid crystals

Novel symmetric and non-symmetric chiral twin compounds possessing one or two thioether groups in a central spacer were prepared, and the effect of substituting oxygen for sulphur on the liquid crystalline properties investigated. Chiral twin compounds possessing an alkylsulphanyl spacer showed an antiferroelectric phase exclusively. However, replacing the alkyloxy chain of the analogous monomer by the alkylsulphanyl chain has no significant effect on the phase transition behaviour, i.e. both of the monomers showed the ferro- and ferri-electric phases as well as the antiferroelectric phase. Thus, different effects of introducing the thioether linkage were for the first time observed between twin and monomeric systems. The introduction of oxygen or sulphur atoms into the central alkyl spacer of the chiral twin was also investigated, and these modifications were found to stabilize the SmA phase. Furthermore, the twin compound possessing a thiaalkyl spacer showed two different molecular assemblies in the smectic A phase.     

Chiral Photoresponsive Tetrathiazoles That Provide Snapshots of Folding States

Herein, we designed chiral photoresponsive tetra(2‐phenylthiazole)s, which induce a diastereoselective 6π‐electrocyclization reaction in a helically folded structure to freeze the conformational interconversions. The folding conformation with one helical turn of tetra(2‐phenylthiazole)s was supported by multiple intramolecular noncovalent interactions including vicinal S???N interheteroatom interactions and CH–π and π–π stacking interactions between nonadjacent units, as found in X‐ray crystal structures as well as quantum chemical calculations. The introduction of a chiral group at both ends of tetra(2‐phenylthiazole) dictates the preferential folding into a one‐handed helix conformation by the simultaneous operation of S???O and multiple CH–π interactions that involve the chiral end groups. Since the tetra(2‐phenylthiazole)s possess two equivalent photoreactive 6π‐electron systems and the folded conformation is suitable for photoinduced electrocyclization reaction, they undergo a photocyclization reaction in a stereoselective manner to memorize the chirality of the helix in a resulting diastereomeric closed form.     

Synthesis of 4,5-fused tricyclic quinolines via an acid-promoted intramolecular Friedel–Crafts allenylation of aniline derivatives

A novel method for synthesizing 4,5-fused tricyclic quinoline derivatives based on an acid-promoted intramolecular Friedel–Crafts allenylation of anilines. Using aryl group-substituted propargyl alcohol derivatives with a meta-substituted N-Boc aniline unit as substrates, a four-step reaction sequence involving an acid-promoted intramolecular Friedel–Crafts allenylation of anilines, an acid-promoted intramolecular C–N bond formation, deprotection of the Boc group, and air oxidation proceeded in a single pot, producing the corresponding 4,5-fused tricyclic quinoline derivatives in 31–84% yield.     

Development of a fluoride-responsive amide bond cleavage device that is potentially applicable to a traceable linker

A fluoride-responsive (FR) amino acid that induces amide bond cleavage upon the addition of a fluoride was developed, and it was applied to an FR traceable linker. By the use of an alkyne-containing peptide as a model of an alkynylated target protein of a bioactive compound, introduction of the FR traceable linker onto the peptide was achieved. Subsequent fluoride-induced cleavage of the linker followed by labeling of the released peptide derivative was also conducted to examine the potential applicability of the FR traceable linker to the enrichment and labeling of alkynylated target molecules.     

Biological responses to silicon and nitrogen-rich PVD silicon nitride coatings

Most structural bioceramics are comprised of metallic oxides such as alumina and zirconia. They are generally considered to be completely bioinert, but a non-oxide ceramic, silicon nitride, achieves equivalent levels of mechanical reliability while being bioactive. Silicon nitride can not only stimulate cellular proliferation but it is also antipathogenic with demonstrated efficacy against Gram-positive and Gram-negative bacteria, fungi, and viruses. In this work, three physical vapor deposition coatings with different Si:N ratios (silicon-rich, stoichiometric, and nitrogen-rich) were deposited on mirror-polished silica glass substrates. The coatings were characterized by spectroscopic and microscopic techniques and tested in vitro against E. coli and KUSA-A1 mesenchymal cells. Results showed that nitrogen-enriched Si_xN_y has a strong antibacterial effect against E. coli and contributes to cellular proliferation while silicon-enriched Si_xN_y stimulates the production of bone tissue, with higher indexes for mineralization and quality. These results suggest that Si_xN_y's biological properties can be optimized for specific applications by carefully tuning its surface chemistry.     

Quantification of Intracellular Thiols by HPLC-Fluorescence Detection

Biothiols, such as cysteine and glutathione, play important roles in various intracellular reactions represented by the redox equilibrium against oxidative stress. In this study, a method for intracellular thiol quantification using HPLC-fluorescence detection was developed. Thiols were derivatized with a thiol-specific fluorescence derivatization reagent, viz. ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F), followed by reversed-phase separation on an InertSustain AQ-C18 column. Six different SBD-thiols (homocysteine, cysteine, cysteinylglycine, γ-glutamylcysteine, glutathione, and N-acetylcysteine as an internal standard) were separated within 30 min using a citric buffer (pH 3.0)/MeOH mobile phase. The calibration curves of all the SBD-thiols had strong linearity (R² > 0.999). Using this developed method, the thiol concentrations of human chronic myelogenous leukemia K562 cell samples were found to be 5.5–153 pmol/1 × 10⁶ cells. The time-dependent effect of a thiol scavenger, viz. N-ethyl maleimide, on intracellular thiol concentrations was also quantified. This method is useful for elucidating the role of intracellular sulfur metabolism.