A meal of carefully prepared puffer fish, which hopefully does not contain the toxic livers and ovaries, tests the courage of gourmets and cooks. Tetrodotoxin (formula shown), the poisonous principle of the puffer fish, presents a challenge for synthesis, which has been mastered by three teams using different strategies and key steps.

Survival of the fittest describes a new method for screening dynamic combinatorial libraries. A mixture of dipeptides is tested for binding to a target protein, and the weaker binding compounds are destroyed by pronase. The released components are then recoupled to regenerate the library. By repeating this cycle of selection, destruction, and regeneration, a small binding preference eventually results in a large enrichment of the tightest binding compound. Photo credit Douglas Jager (http://www.mindspring.com/~bjager/akpix2.html).

OC without CO: Innovative strategies for solving the drawbacks associated with the handling of toxic, gaseous carbon monoxide in carbonylation reactions are described. These strategies, some of which are shown schematically, highlight a variety of experimentally simple and safe tools for carbonylation that will be useful to synthetic organic chemists.

Collected and combined: A strategy for guiding the search for new chemical reactions is described by giving concrete examples from the many years of research from the authors group. Three major research topics—oxidative–reductive condensation, the Lewis acid catalyzed aldol reaction, and glycosylation of glycosyl fluoride—are described to show how the initial concept was formulated and then expanded into broadly applicable methods.

Magnetism gets a new twist: The crystal structure and magnetic properties of a chiral 3D ferrimagnet with T_c of 35 K, [{Cr^III(CN)₆}{Mn^II(d- or L-NH₂ala)}₃]⋅3 H₂O (NH₂ala=aminoalanine ion) are described. The complex has an extended, chiral, triple-strand helical arrangement of Mn^II ions, formed by the coordination of the organic ligands (see picture; purple Mn, gray C, blue N, red O). The triple helixes are linked to each other by the {Cr^III(CN)₆} units.

Simple banana-shaped organic molecules self-organize into finite, spherical coordination networks with a diameter of up to 7 nm (see structure; green Pd, red O, blue N, gray C). These molecular spheres consist of 12 equivalent metal centers and 24 equivalent ligands and have cuboctahedral symmetry. Functional groups (C₆₀ or porphyrin) attached to each ligand are aligned equivalently at the periphery of the sphere.

Surface replication: Three-dimensional ordered colloidal crystals are used as templates in creating surface gratings from a large variety of functional materials, such as metals, semiconductors, and dielectrics, provided that the material deposition only occurs on the periodic surfaces of the templates. By this nonlithographic technique wafer-scale samples with submicron periodicity can be rapidly created (see picture).

A compound with potential: The title compound (see structure) not only resembles the relevant protein active sites geometrically and spectroscopically, but also possesses the least negative [Fe₄S₄(L)₄]^2−/3− and [Fe₄S₄(L)₄]^3−/4− (L is a monoanionic ligand) redox potentials of all protein Fe₄S₄ analogues. The value of the Fe₄S₄^+/0 redox potential implies a new route to the isolation of the elusive Fe₄S₄⁰ cluster.

Container crushing: Thermal liberation of the encapsulated guest in a cryptophane has been shown to cause conformational “implosion” in the solid state. The resulting collapsed form is kinetically stable, can be isolated, and its unexpected structure has been elucidated by X-ray diffraction. It eventually re-inflates, however, to the occupied container-like species on standing in solution (see scheme).

Sensitive and selective, a modular-based fluorescent polymer combines a rigid electron-conducting block (see picture; B) with a flexible binding block (A). The monopyridyl group of the coordinating module has a great affinity for Pd^II ions and selectively binds them through self-assembly. Thus, the fluorescent conjugated polymer may be used for sensing Pd^II ions.

Finding the right angle: The contact angle of nanoparticles at the water/oil interface can be engineered close to 90° by capping with ligands containing carboxylic ester terminal groups. This drives the nanoparticles to self-assemble into close-packed films (see picture), and thus provides the opportunity to create two- or three-dimensional homo- or heterogeneous nanostructures for electronic, optoelectrical, and magnetic applications.

The selective cleavage achieved by activated caspase-8 has been mimicked by using a photofunctionalized caspase-3 having 2-nitrophenylglycine (Npg) at a specific position of the peptide chain (see picture). The study shows that the activity of caspase-3 has been clearly expressed by photoirradiation and that autocleavage of caspase-3 has been suppressed by the site-selective incorporation of the Npg residue.

The best of both worlds: The synthesis of carbon-encapsulated iron-based magnetic nanoparticles is described (see picture: left TEM image, right model). With such small catalysts that have macroscopic magnetic properties, the advantages of homogeneous or colloidal and heterogeneous catalysts can be combined.

Maximally helical polyalanines, 9 to 24 residues in length, are used to calibrate the assignment of fractional helicity (FH) from circular dichroism ellipticities. Water-solubilizing, helix-stabilizing N- and C-caps induce FHs>0.9 in core polyalanine regions. Linear length regressions of peptide molar ellipticities (blue-green curves) yield slopes (red arrows) that define molar per-residue ellipticities of a fully helical alanine residue (red curve).

Spontaneous formation of microspheres is observed when charged poly(amino acid)s are combined with certain oppositely charged, multivalent organic ions. The surfaces of the spheres are chemically active and act as templates for silica condensation, and the assemblies can be made hollow or polymer-filled, depending on the silica precursor (see image; the fluorescent polymer forms a layer inside a colloidal-silica-coated sphere).

There's nothing confusing about the dimer (see picture) that forms from N-confused porphyrin! The dimer was obtained as a directly β–β-linked structure through a simple acid-catalyzed condensation reaction of the monomeric macrocycles, and the electronic interaction between the porphyrin subunits was studied for both the free-base form and for the bis(nickel(II)) complex.

A high-nitrogen compound, 3,6-di(azido)-1,2,4,5-tetrazine, was used as precursor for the preparation of carbon nanospheres (see SEM picture) and nitrogen-rich carbon nitrides. The conversions into both carbon-based materials are simple, occur under mild conditions (low temperature, no applied pressure), and require no vacuum systems, extraction, carbonization, and purification.

The structure and reactivity of high-valent Fe^VO and Mn^VIO oxidation catalysts containing a polyoxometalate [PW₁₁O₃₉]⁷⁻ lacunary ligand (2) have been investigated by a computational study. Calculations have demonstrated there is an intriguing analogy between these species and the active species (1) of the enzyme cytochrome P450 (see scheme).

Ions in cages: Hydrothermal reactions give two novel 3D heterometallic frameworks, [{[Gd₄(ip)₇(H₂O)₂][Cu(bpy)₂]₂}_n] (1, bpy=2,2′-bipyridine, H₂ip=isophthalic acid; see structure, space filling models: [Cu(bpy)₂], polyhedra: Gd) and [{Gd₃Cu(ip)₅(Hip)(bpy)}_n]⋅n H₂O (2). The structure of 1 consists of charged cages containing two encapsulated Cu^I complex cations, whereas that of 2 contains charged cavities in which Cu^II complex cations are bound.

The length and high flexibility of the linker in a heterodinuclear ruthenium–platinum complex (see X-ray crystal structure) enables the platinum unit to independently interact with DNA by π–π stacking or coordination, possibly after pre-association of the 2+ charged ruthenium unit. A prototype of this challenging class of potentially cytostatic compounds is presented.

A low turn-on voltage is revealed by repeating field emission tests of NbS₂, which is a highly reliable field emitter. Well-defined NbS₂ nanowires (see picture) can be generated in the bulk by direct heating of Nb and S powders in sealed quartz tubes in the presence of I₂.

Transfer interference: Synthesis of the bisubstrate-type N-acetylglucosaminyltransferase (GnT) inhibitor 1 was achieved by a polymer-resin hybrid capture–release strategy for the construction of the acceptor component. One-pot ligation in aqueous media produced the coupling product, and subsequent construction of a diphosphate linkage led to 1. Inhibitory activities toward GnT-V and GnT-IX were evaluated and revealed the potency of 1 toward the latter enzyme.

A Sharpless asymmetric dihydroxylation of the commercially available building block 1 affords the common chiral intermediate 2 for the synthesis of the fluorinated monosaccharides 3–5 (Bn=benzyl).

A practical and scalable operation: The reaction shown in the scheme, which uses catalytic amounts of hexacarbonyldicobalt, gives access to versatile bicyclic systems, which until now could only be obtained in low quantities by a photochemical process starting from tropolones. An isolation of the primary Pauson–Khand products is not necessary.

PC bonds mimic CC bonds in the radical-initiated copolymerization of a phosphaalkene 1 and styrene (see scheme). The resulting copolymers 2 have unprecedented phosphine-containing backbones with phosphorus compositions that vary depending on the monomer ratios. These novel functional hybrid inorganic–organic macromolecules are used as polymeric supports for the Pd-catalyzed Suzuki coupling. VAZO=1,1′-azobis(cyclohexanecarbonitrile).

In control! Ag₂S nanocrystals of predictable size and shape were synthesized from the precursor Ag(SCOPh) in the presence of an amine. Careful tuning of several parameters, such as the reaction temperature and the ratio of amine to precursor, led to Ag₂S nanocrystals of varying morphology (red: nanocubes; blue: faceted nanocrystals; yellow: nanorods) and size. x=particle size. HDA=hexadecylamine.

A winning combination of metal and ligand: The catalyst formed in situ from Sc(OTf)₃ and bipyridine 1 (10 mol %) mediates the alcoholysis and aminolysis of meso-epoxides in high enantioselectivities and furnishes valuable chiral 1,2-diol monoethers 2 and 1,2-amino alcohols 3 as products (PMB=para-methoxybenzyl).

Two ring closures, a ring opening, and two intermolecular proton shifts are the crucial steps in a cascade reaction that is triggered by the simple deprotonation of alkynylimines and leads ultimately to aminobenzannulation products (see scheme). The reactions proceed in good to very good yield and with excellent chemoselectivity.

Like a chlorinated golf ball aptly describes a new kind of chlorosiloxane particle (Si_xO_yCl_z, CSN; see picture). Under suitable conditions they are formed by the reaction between SiCl₄ and O₂ in the gas phase. The surface of these spherical, amorphous particles is densely covered by chlorine atoms. These can be substituted by nearly any group. Thus, the surface of the particles can be customized for the particular purpose.