Chemistry – An Asian Journal

Affinity chromatography (AC) using ligand-immobilized bead technology is generally the first choice for target exploration. However, a moderately bioactive ligand, such as endogenous bioactive metabolites, is expected to cause difficulties in AC-based target detection because AC is highly dependent to extremely high affinity between ligand and target. As described in their Full Paper on 3286 ff., M. Ueda et al. report that a compact molecular probe (CMP) strategy has proven to be effective for detection of a moderate-affinity target for which AC cannot be applied successfully. We applied this CMP strategy for the target identification of potassium isolespedezate that showed moderate leaf-opening activity (10⁻⁵–10⁻⁶ M). By using this CMP approach, the cytosolic target protein, Cassia obtusifolia MetE, was detected and isolated as a single band.

One-pot hydrogen-bonding-assisted macrocyclizations have received considerable recent interest due to their already proven and other potentially realizable functions and applications. Mechanistic investigations on one-pot macrocyclizations, however, are scarce. In their Full Paper on page 3298 ff, H. Q. Zeng et al. demonstrate, for the first time, the applicability of a chain-growth mechanism to the POCl₃-mediated one-pot macrocyclization reaction, allowing for the highly selective formation of five-residue macrocycles formed by the successive addition of bifunctional monomer units onto the growing oligomeric backbone.

A little common sense goes a long way! Recurrent motifs and patterns of various elimination reactions in organic synthesis are discussed. We derive and exemplify heuristic guidelines for describing and predicting elimination reactions with classical and contemporary transformations. Heuristic principles allow an easier classification of reactions, bring order to diversity, and encourage a change in how we teach and perceive organic chemistry.

Regio- and stereoselective addition of a silyl-substituted alkynyl sulfide to various terminal alkynes proceeds in the presence of a palladium catalyst to give (Z)-1-thio-1,3-enynes, which are useful building blocks for the synthesis of polysubstituted 1,3-enynes. Addition to internal alkynes also takes place under solvent-free conditions (see scheme).

Have you been framed? Mesoporous monocrystalline K_0.8Ti_4.3Fe_3.7O₁₆ cubes have been prepared by a sophisticated crystal transformation from a single-crystalline titanium-containing Prussian Blue analogue. This is a new strategy for the design of fully crystallized frameworks in mesoporous materials (see graphic).

Free metal jacket: A regioselective metal-free synthesis of polysubstituted pyrroles has been developed through a (diacetoxyiodo)benzene-mediated cascade reaction of alkynyl amines in moderate to good yield (see scheme).

Getting organized: The chirality organization of polyaniline-unit molecules was achieved by the introduction of pendant amino acid groups through intramolecular hydrogen bonding; these groups play an important role in the stabilization of the chirality-organized redox species.

TA for now: Tethered aminohydroxylation (TA) cyclic stereocontrol is possible in the catalytic TA reaction of acyclic systems that bear an exocyclic stereodirecting group. The influence of the alkene substitution pattern and the role of the protecting group on the allylic alcohol are both explored. A model is also presented to rationalize the observed trends in stereoselectivity.

Splinter Cell: Organic photovoltaic cells using bis(5,7-dimethyl-8-hydroxyquinolinato)platinum(II) [Pt(Me₂q)₂] showed the best performance (η_P=2.4 %) among the other [Mq₂] or [M(Me₂q)₂] complexes prepared in this work. The crystal structures together with the GIXRD data of thin films of these metal(II) complexes revealed that both the peripheral methyl substituent(s) and Pt^II ion play pivotal role to the performance of the FETs and OPV cells.

Metal-insulator transition: Beta-K_0.33V₂O₅ nanorods have been synthesized by hydrothermal methods. The temperature-dependent resistivity and magnetization both have shown metal–insulator transitions at about 72 K for beta-K_0.33V₂O₅, rendering it as a new member of the beta-A_0.33V₂O₅ bronze family.

Pores and windows! High-molecular-weight polystyrene-block-poly(ethylene oxide) diblock copolymer (PS-b-PEO) was utilized as colloidal spheres in the presence of water. Adequately thick films with multilayers of spherical macropores were fabricated in one-pot. The macropores (30–200 nm) were homogeneously distributed over the entire film and the pore windows between the macropores were tunable (up to nearly 10 nm) by changing the relative amount of PS-b-PEO in the precursor solutions.

Simplicity through complexation: Tricarbonyliron complexes of dendralenes are readily prepared and stable. They allow the formation of products that cannot be accessed directly from dendralenes, including unprecedented structures (see scheme).

Ace of base: 5-(Pyren-1-yl)uracil behaves as a base-discriminating fluorescent nucleobase in a pyrrolidinyl acpcPNA system with an alternating proline/2-aminocyclopentane carboxylic acid backbone. The fluorescence enhanced significantly upon pairing with adenine in the complementary DNA target.

Bulking up! Combining the concepts of supramolecular polymers with dendronized polymers provides an avenue to create bulky polymers with easy structural modification and tunable properties. The synthesis of a novel class of side-chain supramolecular dendronized polymethacrylates through a host–guest interaction, which show characteristic thermoresponsive behavior in the temperature range of 30–52 °C, is described.

MOFs for gas! A strategy is proposed for the evaluation of MOFs for gas-based applications which involves thermal treatment, water stability, and gas sorption. Investigations on the zirconium-based metal–organic framework, UiO-66, show this material to be stable to water and to possess physical properties comparable or better than the reference zeolite, NaY.

The selective recognition/extraction behavior of single-walled carbon nanotubes (SWNTs) with specific chirality was investigated using a poly(dihydrophenanthrene), whose chemical structure is different in the non-aromatic ring numbers from that of poly(fluorenes).

Affinity chromatography by using ligand-immobilized bead technology is the first choice for target exploration of a bioactive ligand. However, when a ligand has comparatively low affinity against its target, serious difficulties will arise. Herein, we report that the use of a compact molecular probe (CMP) will be advantageous in such cases (see scheme).

Adding one by one: POCl₃-mediated one-pot macrocyclization allows the highly selective formation of five-residue macrocycles that proceeds by a chain-growth mechanism in which the successive addition of a bifunctional monomer unit onto either another monomer or the growing oligomeric backbone is faster than other types of bimolecular condensations involving oligomers longer than monomers (see scheme).

The first airbender: Li–air chemistry represents the highest energy density in chemical energy storage. A rate capability of 10 mA cm² is demonstrated for the first time for the gas-diffusion electrode in nonaqueous electrolyte. The advancement could lead to a major improvement in Li–air technology.

An electrochemically highly amphoteric nanographene 1 was synthesized and characterized experimentally and theoretically. The synthetic strategy involves the attainment of a tetrathiafulvalene (TTF) derivative with two diamine moieties, which also plays a crucial role in the development of diverse TTF-based functional materials. The direct fusion of ovalene units with the TTF core dramatically enhances the intermolecular π–π interactions (see graphic).

Two′s company: The electronic coupling between two amine redox sites bridged through the 5,5′-positions of the [Re(CO)₃Cl]-chelated 2,2′-bipyridine was studied by electrochemical, spectroscopic, and EPR analysis. Interestingly, multiple near-infrared bands were observed in this new organic mixed-valence system. The results are interpreted with the aid of DFT and TDDFT calculations.