Angewandte Chemie International Edition

An isolated space for size- or shape-selective dynamic molecular recognition and metal-triggered chemical reactions is offered by the cavity within nanocapsules. In their Communication on page 6488 ff., M. Shionoya and co-workers describe a series of isostructural octahedral capsules prepared from a common tridentate ligand and ten different transition-metal ions, as highlighted in green in the cover picture, and demonstrate site-specific exchange of the anions coordinated within the cavity to the metal centers.

Bonds activated: In recent years, CH insertion by metal-bound carbenes or nitrenes has come to the forefront as the most promising approach for the development of practical intermolecular methods for selective CH functionalization. Recent examples demonstrate the spectacular regio-, diastereo-, and enantioselectivity that is possible in this methodology.

Exploring orientation: With the help of atomic force microscopy, the linkage and orientation of covalently bound surface molecules can be investigated (see picture). Nebel and co-workers applied this technique to the characterization of DNA films covalently bound to a diamond surface for the first time.

Down to the wire: Despite the recent remarkable progress in the chemistry of conjugated polymers, the synthesis of conjugated polymers that contain cyclophane units in the main chain (see picture) is limited. The Minireview discusses the synthesis and properties of through-space conjugated polymers based on cyclophanes and gives insight into their potential applications, for example, as molecular wires.

Front and center: The tumor-suppressor protein p53 is the central element of the control system that many cells use to prevent the development of cancer. An intact p53 network ensures that DNA damage is detected early on. In-depth concepts and the newest advancements in the understanding of the structure and regulation of p53 are discussed. The picture shows the binding of the DNA binding domain of p53 (blue) to the DNA consensus sequence (orange).

Self-sacrifice: Poly(acrylic acid) was used to tune the diameter of 1D nanowires prepared from linear Cd²⁺/thioglycolic acid coordination polymer chains. The nanowires were then employed as sacrificial templates for preparing long CdTe nanotubes of different diameters (see the TEM images).

Through-bond coupling across a cyclodiborazane core results in large absorption cross sections in a new type of boron-containing two-photon-absorbing chromophore (see picture; B pink, N blue, C gray, H other than BH (white) omitted). This is a first step in the design of new dual-property chromophores for applications in biological science or medicine (e.g., two-photon imaging and boron neutron capture therapy).

In a different light: A photoinduced change in surface morphology provides reversible changes in the superhydrophobic properties of a photochromic diarylethene film. The effect is achieved by the reversible formation of fine fibril structures on the coated microcrystalline surface upon irradiation by UV or visible light (see picture).

Fully reversible crystal photochromism between the μ-O₂SSO₂ (1) and μ-O₂SOSO (2) forms of a dinuclear rhodium complex has been observed. The photochromic reaction, including stereoselective oxygen-atom transfer and stereospecific transformation of photochemically generated μ-O₂SOSO isomers into the most stable isomer, was directly followed by conventional single-crystal X-ray diffraction.

Nature's route for amyloid prevention: Insulin is a natural inhibitor of amyloid formation by the islet amyloid polypeptide (IAPP). The interacting domains of both proteins were identified by using a reductionist approach (see scheme). An understanding of the molecular mechanism of this physiological interaction may lead to the design of peptidomimetic drugs for type II diabetes.

Let's twist again: Actinide quadruple-stranded helical supramolecular architectures were synthesized in which two capped square-antiprismatic Th^IV centers are coordinated by four bis(bidentate) 4-acylpyrazolone chelating strands. This example shows a cluster formation caused by incommensurate coordination numbers.

The sweet-test thing! Carbohydrate discrimination is highly challenging as a result of the similarity in their functional groups. A series of pH sensor/pH change inducer ensembles has been developed as an artificial “tongue” for the identification of carbohydrates. The optimized sensor array with six probe pairs demonstrated full discrimination of 23 carbohydrates.

Ten of a kind: A series of {M₆L₈} octahedral metallocapsules that are structurally identical except for the metal at the apexes was quantitatively prepared from tris-monodentate ligands L and ten divalent d⁵–d¹⁰ transition-metal ions (see picture). Six CF₃SO₃⁻ anions coordinated inside the capsules can be site-selectively replaced with other anionic ligands to functionalize the cavity.

Going straight: A luminescent composite of poly(p-phenylenevinylene) (PPV) and amylose was synthesized by direct polymerization of the precursor monomer in aqueous media in the presence of amylose. The PPV–amylose composite consists of a rigid-rod PPV segment threaded into a flexible amylose tube and self-assembles into liquid-crystalline phases.

In the pocket: A nanoporous framework with internal surfaces lined with amino acid residues (see structure; Ni cyan, C gray (chiral centers yellow), H white, N blue, O red) is produced by the pillaring of nickel–aspartate layers by 4,4′-bipyridine. The presence of pockets capable of multiple interactions with guest species permits the enantioselective sorption of short-chain diols.

A very good host: The guest acid molecules of hydrothermally synthesized [V(O)(bdc)](H₂bdc)_0.71 (bdc=benzenedicarboxylate) are removed to give high-quality single crystals of [V(O)(bdc)] (1). On absorption of guest molecules from the liquid phase, 1 undergoes crystal-to-crystal transformations (aniline: 2; thiophene: 3; acetone: 4). Furthermore, complex 1 also selectively absorbs thiophene and dimethyl sulfide from methane.

Going bananas: In a twisted geometry, an extrinsically chiral supermolecular structure was obtained in the calamitic phase. Upon cooling down to form the B_x phase, imbalanced growth of an intrinsic preferential chiral structure was attained. The preferential chiral handedness of the banana mesophase can be also controlled by the handedness of the twisted configuration.

Unusual storage: An organic nonporous material, p-tert-butylcalix[4]arene, sorbs acetylene with high storage density under ambient conditions. It is presumed that gas molecules diffuse through the seemingly nonporous lattice without disrupting the arrangement of the host molecules (see picture; red O, blue C, gray H, yellow void space).

Two in one: An equimolar mixture of the diastereomers (1R,2S,5R)-MenMgCl and (1S,2S,5R)-NeomMgCl is formed from reaction of Mg with either menthyl (Men) or neomenthyl (Neom) chloride. Once formed, each component of the Grignard reagent is configurationally stable. Reaction with electrophiles generally yields products from attack by the more nucleophilic menthyl portion of the Grignard reagent.

Com-paring mechanisms: The so-called hydrocarbon pool mechanism does not operate with zeolite ZSM-22 in the methanol-to-olefin (MTO) conversion process as a result of the narrow channels (0.57 nm) in its framework structure. However, this provided a condition free of secondary reactions for detailed mechanistic studies, with H/D exchange patterns of toluene suggesting a paring mechanism.

Putting two and two together: An ordered mesoporous silica crystal of the cage type with cubic Fmm symmetry was prepared by using a gemini surfactant as template. Icosahedral, decahedral, and plate morphologies are discussed (see SEM image). The structure is explained by the occurrence of multiple twinning during the formation of mesostructures.

An open relationship: The triethylborane/O₂-mediated addition of xanthates to vinyl epoxides and derivatives represents an efficient process to form carbon–carbon bonds. Complex structures can be rapidly assembled in a modular, convergent manner, under mild conditions, using readily available reagents (see scheme, Bn=benzyl). The formation of quaternary centers proved especially facile.

A good alternative: Highly reactive catalysts based on palladium and dialkylbiarylphosphino ligands provide unprecedented reactivity and selectivity in CN bond-forming processes. The bulky monophosphine catalyst system Pd/1 was effective for the reaction of aryl/heteroaryl halides bearing primary amides and 2-aminoheterocycles (see scheme; dba=dibenzylideneacetone, R=CONH₂, NH₂), thus showing that monodentate phosphines are viable alternatives to, and sometimes superior to, chelating ligands.

Ocean's three: Unearthed from the bottom of the ocean off the coast of La Jolla (California, USA), marinomycins A–C, which differ in geometry about the C8C9 and C8′C9′ double bonds, have been prepared by total synthesis through a strategy that features a Suzuki coupling reaction to forge their remarkable polyunsaturated 44-membered-ring systems (see picture).

Carbonyl ylides to the fore: the first total synthesis of polygalolides A (1) and B (2) has been achieved by exploiting a tandem carbonyl ylide formation/1,3-dipolar cycloaddition to construct the unprecedented 5,10-dioxatricyclo[6.2.1.0]undecane core structure of these molecules in a single step.

Caught between two geometries: The solid-state structure of [NEt₄][AuCl₂][AuCl₃] (see picture) shows a geometry in AuCl₃ that is representative of a Y-shaped transition state as a result of Jahn–Teller distortion. Calculations by others indicate that the observed orientation is an intermediate geometry between two T-shaped structures with C_2v symmetry.

Adsorption structures of multifunctional molecules: A DFT study of four conjugated molecules on six metals showed that molecule–metal vibrations correlate with adsorption structure and strength (see picture). The η²μ₁ structure on Ag and Au is weakly adsorbed and has softer vibrations, but the η⁴μ₃ structure on Ni, Pd, and Pt is strongly stabilized and these modes are strengthened. An intermediate η³μ₃ structure occurs on Cu.

Three in one: The oxidation of methane to methyl derivatives, conversion of the methyl derivatives into oxygenated compounds, and regeneration of the oxidation media are the three steps involved in the catalytic partial oxidation of methane by MoO₂Br₂ supported on Zn-MCM-48 (see scheme). Reversible bromine metathesis between MoO₂Br₂ and MoO₃ is key to the efficient catalytic process.

Ring cycle: Iron and manganese corroles are among the most efficient decomposition catalysts of peroxynitrite reported to date. The catalytic rate of the iron complex is higher than that of analogous porphyrins, and the manganese complex operates through the catalytic disproportionation cycle shown in the picture.

Zinc twice: Naphthalene is attacked and doubly deprotonated at the 2,6-position by a synergic sodium zincate base to generate a centrosymmetric dizincated molecule. The approach of alkali-metal-mediated zincation can effect dimetalation as well as monometalation of polycyclic aromatic hydrocarbons, thus providing access to new zincated naphthalenes that are inaccessible directly through mainstream organozinc reagents.

The clash of hybridizations: A tailored phase-transfer organocatalyst merges sp³- and sp²-hybridized carbon atoms by catalyzing the first enantioselective vinylic substitution (see scheme; EWG=electron-withdrawing group). The method provides access to optically active compounds possessing vinyl-substituted quaternary stereocenters with control of the alkene configuration.

Belt holes: By heating chromium under an ethanol atmosphere, nanobelts and nanorods of oxygen-deficient chromia (Cr₂O_3−x) are prepared for the first time (see image). The nanobelts exhibit two types of superlattice structures that arise from different orderings of the oxygen defects. Folding observed in some of the nanobelts is a result of twinning.

Rings from light: Irradiation of acetonitrile solutions containing 1-cyano-2-(4-pentenyl)naphthalene derivatives afforded benzotetra- and benzopentacyclic compounds with tri- and tetraquinane skeletons in high yields, through intramolecular [2+3] photocycloaddition of the alkene at the 2,4-positions of the cyanonaphthalene (see scheme; n=1, 2). The structures of these adducts were confirmed by their spectral properties and by X-ray crystallographic analyses.

Three into one will go! A three-component coupling of a hydroxylamine, an aldehyde, and a cyclopropane diester provides the tetrahydro-1,2-oxazine scaffold necessary for completion of the first total synthesis of the natural product phyllantidine.

Mimicking sponges: Well-defined crystalline nanoparticles of cubic BaTiO₃ are prepared at a very low temperature by using a bio-inspired methodology. A bimetallic alkoxide is used as a single-source precursor in a vapor-diffusion sol–gel synthesis. Water and catalyst (HCl) are delivered in a spatial and temporal gradient to promote the slow growth of nanoparticles.

Racemization wanted: The dynamic kinetic resolution of secondary alcohols can be achieved by a simple and readily available catalyst system. Substrate racemization is effected at room temperature by a combination of (racemic) 1,1′-bi-2-naphthol (binol) or 2,2′-biphenol with AlMe₃, and a lipase performs enantiospecific acylation (see scheme).

DNA alkylation: The reactivity and selectivity of DNA-alkylating duocarmycin analogues were determined by direct ESI-FTICRMS (negative-ion mode) measurements. The high efficiency of a new seco drug for the alkylation of duplex DNA has been determined in this way for the first time (picture: drug bound covalently to an oligodeoxynucleotide). The corresponding, less toxic prodrug and the enantiomer of the seco drug show, in contrast, only a very low alkylation tendency.

Better and better: The glycosidic prodrug (+)-1, which is based on duocarmycin antibiotics, was synthesized for selective cancer therapy. The drug was developed within the context of “antibody-directed enzyme prodrug therapy” (ADEPT). As a result of its outstanding QIC₅₀ values, its excellent solubility, and easy synthesis it exceeds all other prodrugs produced to date. QIC₅₀=comparative toxicity value between the prodrug and the drug.

Designer jackets: Polydentate amino-functionalized poly(ethylene oxide)s with various block lengths are synthesized and used for ligand exchange and phase transfer of quantum dots and magnetic nanoparticles (see scheme; TEM images of the particles before and after the exchange are also shown). The ligands enable the transfer of the previously water-insoluble particles into aqueous media.

Sweet traitor: Monoclonal antibodies against a tetrasaccharide that contains the unique monosaccharide anthrose, which is found on the surface of B. anthracis spores, are used to selectively detect this biowarfare threat.

Alternative mimetics: Short cyclic hexapeptides (see picture; blue N, red O, white H, gray C) can be effective for oligosaccharide mimicry. The individual contributions of cyclization, amino acid stereochemistry, turn position, and side-chain functionality to the glycomimetic properties of the peptides were identified. Two peptides proved to be high-affinity ligands for the 412 antibody and also showed enhanced functional activity as HNK-1 mimetics.