Recent progress in chemical biology research has accelerated the target protein identification of biologically active small molecules, including naturally occurring ligands. It is widely recognized that a biologically active natural product functions as a “key” that fits a specific protein “lock.” However, recent studies have revealed multiligandable nature of natural products that works as “multiple keys” (or a “master key”) fitting multiple “locks” in a biological event. Biological experiments using natural products as ligands have often provided puzzling results, which can likely be attributed to their multiligandability. Thus, a novel research direction dealing with multiliganbale natural product ligand based on their target identification is strongly desired. This review focuses on the current status of natural products chemistry based on their target identification, and suggest the future direction, named chemical biological chemistry (Chem-Bio-Chem).
Novel anionic and lipophilic polymer networks have been successfully synthesized by imine formation between tetraphenylborates and 1,4-phenylenediamine. The obtained polymer networks showed various morphologies depending on the dielectric constant of media used in the synthesis. Moreover, the addition of water led to polymer networks with spherical structure presumably due to suppression of imine formation.
Polydopamine (PDA) bearing surface catechol groups on a silicon wafer was used to induce the deposition of thin TiO2 films from aqueous solution. Different deposition conditions, such as the concentration and pH of precursor solution as well as the deposition temperature, were adopted. It was found that the growth rate and crystalline phase can be controlled by these deposition parameters; moreover, the crystal growth and adhesion strength to the substrate of TiO2 film can be promoted by PDA layer.
Stabilization energies at enol, keto, and transition state structures of 2-(2-hydroxyphenyl)benzimidazole in several types of solvents are systematically examined by quantum chemistry calculations. The solvent effects on the stability of keto are discussed and it has been shown that the keto form on the ground state does not have a local minimum in any type of solvents.
2,3,6,7-Tetrapropoxy- and 2,6-dipropoxy-substituted 9,10-anthraquinone (AQ) and anthracene (ANT) derivatives were synthesized, and their optical properties in solution and in the solid state were investigated. In AQs, the tetrapropoxy derivative exhibited a red shift of absorption in comparison with the dipropoxy derivative and ANT. In contrast, in ANTs, the dipropoxy derivative exhibited a red shift of absorption and fluorescence in comparison with the tetrapropoxy derivative and ANT. The electronic effects of alkoxy substitution could be explained by TD-DFT calculations.
Hollow core–shell particles of titania core and silica shell were synthesized by multistep process, and the core–shell particles showed improved stereoselectivity in the photocatalytic redox-combined synthesis of L-pipecolinic acid from L-lysine in an aqueous suspension without reducing the original activity of the bare titania core.
Hybrid materials of ultimately minimized metal particles, namely, isolated atoms or subnano-sized particles, on thermally exfoliated graphene oxide sheets were produced using cation-exchanged highly oxidized graphite as a precursor. Rh atoms on graphene sheets arrange with a regular spacing of 0.50 or 0.45 nm and form square or rectangular grid patterns, whereas isolated Pt atoms disperse on graphene sheets randomly.
To improve the interfacial compatibility between graphene and poly(methyl methacrylate) (PMMA), amino-functionalization was applied to the graphene oxide via chemical modification using ethylenediamine (EA) and 1,6-hexanediamine (HA). Experimental results showed that with the incorporation of only 1 wt % amino-functionalized graphene oxide (AGO), the thermal stability, mechanical properties, and the dispersibility of fillers in the nanocomposites were improved significantly. The effect of the alkyl chain length of the diamine was also considered.
Uniform Fe3O4 nanospheres have been synthesized by a simple ethylene glycol–H2O system without adding any additives. The average diameter of the Fe3O4 nanospheres was 120–190 nm, and the nanospheres are formed by nanoparticles of several tens of nanometers. The presence of a certain amount of deionized water and the controlled reaction temperature plays an important role in the formation of the Fe3O4 nanospheres. The formation mechanism of the nanospheres is discussed on the basis of the experimental results.
One-pot regio- and stereospecific synthesis of chitoheptaose ((GlcNAc)7) has been achieved by using chitopentaose ((GlcNAc)5) and chitobiose ((GlcNAc)2) as starting materials. The key intermediate, 1,2-oxazoline derivative of (GlcNAc)5, could be directly prepared in water and successfully transglycosylated to (GlcNAc)2 catalyzed by a mutant chitinase with lower hydrolyzing activity.
A nonanuclear nickel(II) cluster, [Ni9(H4L)2(OMe)6(OAc)10(H2O)4]·14H2O (1·14H2O), was synthesized by the reaction of an amide ligand H5L (= 2-hydroxy-4,6-dimethyl-N1,N3-bis(2-hydroxyethyl)-1,3-benzenedicarboxamide) with nickel acetate in the presence of triethylamine. The cluster molecule consists of two cubane units and a mononuclear central moiety, connected by acetate bridges. In the cubane cores, ferromagnetic interactions between nickel ions were operative, and the total spin ground state was S = 7 due to ferrimagnetic interactions between the two ferromagnetic cubane cores and the mononuclear nickel spacer.
The carbonylation mechanisms of allylic alcohol catalyzed by [PdHCl(bppm)] complex were studied using a density functional theory (DFT) method. The results indicate that the catalytic cycle consists of three main steps: alkene insertion, CO insertion, and hydrogen transfer and product elimination. Pathways with a Pd(II) character are more favorable than that with Pd(IV) character. Methanol serves as the proton shuttle in carbonylation and reduces the energy barrier by 15.4 kcal mol−1 below that without methanol assistance.
Electron spin resonance (ESR) study was performed on organic layered films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/pentacene that were fabricated with different deposition speed of pentacene on PEDOT:PSS in order to investigate charge formation at the PEDOT:PSS/pentacene interfaces. Clear increases in ESR signals of not only pentacene but also PEDOT were observed, which are caused by the charge transfer at the interfaces. The charge transfer is prominent at high deposition speed of pentacene, which means that slow deposition speed is suitable for solar-cell fabrication without charge formation.
Condensation reaction of 2-methylresorcinol with m-benzenedicarbaldehyde in the presence of HCl as a catalyst in n-propanol at 90 °C for 48 h proceeded via a dynamic covalent chemistry (DCC) mechanism to afford a triple-ringed arene in 52% yield.
A novel para-benzihemiporphyrazine was synthesized from a stepwise reaction of 1,3-diiminoisoindoline and para-phenylenediamine via a linear [2 + 1]-type compound, whereas its ring-expanded [3 + 3]-type analogue was obtained from a one-pot condensation reaction of the same starting materials.
A highly effective cascade process giving 3-alkenylcoumarins is furnished by a series of reactions involving pallada-arylation of ethyl propiolate with phenols, intramolecular transesterification to 3-coumarylpalladium species, its alkyne insertion, and protonation. [Pd(OAc)2(dppe)] is an effective catalyst for the synthesis of 3-alkenylcoumarins from phenols and ethyl propiolate.
Three types of novel gold nanoparticles containing a different condensed ring in their ligands were prepared. Their thermal stability was found to be much higher than that of typical gold nanoparticles surrounded by long-chain alkanethiols because of strong interligand interaction formed by the condensed rings (π–π stacking). A clear correlation was found between the thermal stability and the strength of π–π stacking.
Gold nanorods were modified with two types of double-stranded DNAs (dsDNA) with different melting temperatures. Irradiated by near-infrared laser light, the modified gold nanorods were heated, and single-stranded DNAs were released faster from the dsDNA with the lower melting temperature. Such combinations of different kinds of dsDNA allow us to construct a two-step release system of different types of oligonucleotides.
A novel iron(II) complex [Fe(py4C)2][Fe(py4C)(NCS)3]2 was synthesized, where py4C stands for tetrakis(2-pyridyl)methane. Spin crossover occurred at 161 K (T1/2). Light-induced excited spin-state trapping was observed when irradiated with 532 nm at 10 K, and the conversion was 89%. The relaxation took place at 58 K on heating.
Nontoxic and inexpensive K4[Fe(CN)6] is first introduced as a cyanating agent to cyanation of arylboronic acids. The present method is simple, practical, and allowed a wide range of substrates including functionalized phenylboronic acids, 1-naphthylboronic acid as well as heterocyclic boronic acids to be smoothly converted into the corresponding products in moderate to high yields.
The irradiation of NIR femtosecond laser pulses to a benzene/water bilayer dramatically enhanced the formation of carbon nanoparticles compared with that in neat benzene. The focusing-position-dependent chemistry and the oxidative mechanism of nanoparticle formation are discussed.
Allophane–titania nanocomposite electrodes were prepared from titanium alkoxide sols dispersing the natural clay mineral allophane. Electrochemical measurements indicated that the oxidative degradation of glucose in the electrolyte enhanced the generation of electricity during UV irradiation. A higher short-circuit current was observed in the photofuel cell using the 0.10% allophane-containing titania electrode than that with the normal titania electrode. Allophane effectively adsorbed the glucose molecules and then transported them to the titania, on which their oxidation induced the electrogeneration.
We screened a colored clone from a metagenomic library derived from the marine sponge Halichondria okadai. We isolated a yellow pigment, halichrome A (1), which was structurally elucidated to be a biindole, exhibited cytotoxicity against B16 melanoma cells and was substituted with an ethyl group. To the best of our knowledge, this is the first report of the isolation of a novel compound from a metagenomic library derived from a marine sponge.
A new chiral stationary phase was designed and synthesized via surface-initiated atom-transfer radical polymerization (ATRP) and click chemistry. Poly(2-methyl-3-butyn-2-yl methacrylate-co-divinylbenzene), poly(MBMA-co-DVB), was grafted on silica surface via ATRP (“grafting-from” technique) first, and then azide-modified β-CD was immobilized on the alkyne of the polymer layer as chiral separation material. Different crosslinking degree of poly(MBMA-co-DVB) was selected to improve the hydrophobicity of silica surface. The materials were packed into a stainless-steel column (150 mm × 4.6 mm i.d.) for high-performance liquid chromatography (HPLC), and evaluated by separation of aromatic and chiral compounds. The result demonstrated that the crosslinked benzene ring in poly(MBMA-co-DVB) can well improve the selectivity and retention time.
Using poly(vinylpyrrolidone) (PVP) as a stabilizing agent graphite nanosheets (GNs) and molybdenum disulfide nanosheets (MNs) were conveniently obtained under ultrasound treatment. The two kinds of obtained nanosheets were detected by transmission electron microscopy (TEM) and atomic force microscopy (AFM) and analyzed by Raman spectroscopy. UV–vis spectrophotometric measurement was performed to test their typical absorption peaks.
Nonwoven fabrics based on composite fibers of TiO2 and poly(dimethylsiloxane) (PDMS) are prepared by electrospinning. Nonwoven fabrics based on TiO2–PDMS fibers are initially hydrophobic and undergo rapid wettability conversion to a superhydrophilic state upon plasma irradiation. Hydrophobicity is rapidly recovered under ambient conditions. This wettability conversion can be repeated by subsequent cycles of plasma irradiation and storage under ambient conditions.
The synthesis of N-tert-butylamides using SO42−/CexZr1−xO2 catalysts under solvent-free conditions is reported. The methodology has several advantages such as reusability of the catalyst, solvent-free conditions, easy workup, and comparable yield of N-tert-butylamides. A variety of aliphatic, aromatic, and acid-sensitive substrates give high to moderate yields of the corresponding N-tert-butylamides. Surface acidities of the catalysts were correlated with the results obtained. To the best of our knowledge, this is the first report of a modified Ritter reaction on SO42−/CexZr1−xO2 using tert-butyl acetate as carbocationic source.
Periodicity of mesoporous silica films with aligned cylindrical pores formed on a substrate with a rubbing-treated polyimide through a sol–gel process can be finely controlled using nonionic surfactants with different alkyl chains. The degree of alignment increases with the alkyl-chain length of the surfactant due to increase in anisotropic hydrophobic interaction between the oriented polyimide chains and the alkyl groups, which is responsible for the alignment.
An oxidative rearrangement of cyclic tertiary allylic alcohols to β-disubstituted α,β-unsaturated ketones by Pt black catalyst with aqueous hydrogen peroxide is described. The reaction proceeds under organic solvent- and halide-free conditions and gives only water as a coproduct. The Pt black catalyst is commercially available and can be reused at least four times.
We added an organic additive 2-amino-2-methyl-1-propanol (AMP) and water to dimethylformamide (DMF) and exfoliated graphite therein to prepare graphene. When the content of AMP was 1.0 vol % and the content of water was 0.4 vol %, the dispersion of graphene was obtained at the concentration up to 0.3 mg mL−1, which was 50% higher than that obtained by directly exfoliating graphite in DMF for 24 h. At the same time, the graphene sheets maintained high quality with little impurity.
We demonstrated that aqueous solutions containing a sulfonated polyaramide exhibited stir-induced chirality detected by circular dichroism (CD) spectroscopy. This phenomenon can be visualized as dynamics of supramolecular structure comprising hydrogen-bonded polyaramides. We further show that the sign of the CD response can be tuned using vortex direction, stirring-rate, and concentration.