Intra- or intermolecular: Abyssomicin C, isolated from a marine bacterium, is a potent polyketide-type antibiotic and a synthetic target of prime importance because it inhibits pathogenic bacteria. In recent independent syntheses by the Sorensen and the Nicolaou groups, intra- and intermolecular Diels–Alder reactions featured as the respective key steps for the construction of the oxabicyclo[2.2.2]octane core.

The direct approach: The direct synthesis of eight-membered carbocycles from acyclic precursors is a preparatively challenging task since entropic and enthalpic factors are unfavorable for the formation of rings of this size. Cyclooctanoids can be prepared successfully from acyclic precursors under mild reaction conditions with the help of ring-closing metathesis.

100 years young: In 2006 the chemistry of α-amino acid N-carboxyanhydrides (NCAs) marks a history of 100 years. The NCAs were used for syntheses of oligo- and polypeptides in numerous ways, and recently have played an important role in the hypothesis of molecular evolution. Peptide block copolymers, liquid-crystalline polypeptides, and the application of polypeptides as drugs or drug carriers are also discussed.

Assembly time: Thin films of [Fe(pyrazine){M(CN)₄}] (M=Ni, Pd, or Pt) coordination polymers were assembled sequentially through coordinate bonding on gold surfaces (see scheme). These multilayers exhibit spin-crossover phenomena with hysteresis at room temperature.

Structure assigned: The revised structure of (+)-hexacyclinol (1) proposed recently was confirmed following the total synthesis of the natural product. The synthesis was designed around the highly stereoselective Diels–Alder dimerization of an epoxyquinol monomer, followed by intramolecular acid-catalyzed cyclization.

Hot spots: Thermally responsive AB diblock copolymers that self-assemble into vesicles at higher temperatures were prepared (see picture). These vesicles can be cross-linked by adding an oppositely charged polyelectrolyte.

Green to the core: Cd_xZn_1−xSe alloy core nanocrystals are synthesized and overcoated with Cd_yZn_1−yS to create core–shell nanocrystals with the ideal wavelength of emission for quantum dot light-emitting device (QD-LED) displays. These (Cd_xZn_1−xSe)Cd_yZn_1−yS core–shell nanocrystals are used to fabricate color-saturated green-emitting QD-LEDs (see picture), which are suitable for display applications.

Hold the mayo! Sandwich complexes containing the arch-shaped Pd₄ chain (upper structure; C blue, Pd orange) or the V-shaped Pd₅ chain (lower) were synthesized and structurally characterized. The bending angles of the Pd chains reflect the p π-conjugated geometry of the template ligands.

Bring on the substitute: Even outside of macrocyclic structures, such as vancomycin, appropriate substitution can give rise to atropisomerism in diaryl ethers. Stereochemical stability about the ArOAr axis at room temperature or above is possible when neither of the rings is symmetrically substituted and when at least one ring carries an ortho tert-butyl group or equivalent.

Unique interactions: Ar′ZnZnAr′ (1; Ar′=C₆H₃-2,6-(C₆H₃-2,6-iPr₂)₂), the dimer Ar′Zn(μ-H)₂ZnAr′ (2), and the unprecedented species Ar′Zn(μ-H)(μ-Na)ZnAr′ (3) were synthesized and fully characterized. DFT calculations show that the ZnZn bonding interactions in 1 differ from those of other ZnZn compounds, and the calculations also indicate a new type of ZnZn bond in 3.

Control through molecular pockets: Calixarene-derived diphosphites provide effective hemispherical crowding about catalytic centers. When used in the palladium-catalyzed alkylation of cinnamyl acetate, regioselectivities higher than 98 % in favor of the linear product are observed. In the rhodium-catalyzed hydroformylation of styrene, these diphosphites lead to phenylpropionaldehyde with selectivities as high as 76 %.

An alternative string theory: The current-versus-potential behavior of metal atom strings (Ni, Co, Cr) is dependent on the strength of the d-orbital coupling along the metal atom chain. Penta- and heptachromium strings each exhibit two sets of primary I–V curves, which depend on whether the CrCr bonds alternate and are localized, or are delocalized (see picture).

Mining new assemblies: A molecular bucket wheel consisting of three β-cyclodextrin units, three tetrahedral tetraaqualithium cations, and a tetravalent metal center has been prepared (see picture). The assembly, held together by a series of hydrogen bonds, is also stable in solution.

Dyeing for sunlight: A new dye CYC-B1 (see picture), with the highest absorption coefficient known so far for Ru-based photosensitizers, was prepared. Solar cells sensitized with CYC-B1 have a very high current density, and the conversion efficiency of CYC-B1 is 10 % higher than that of cis-di(thiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylate)ruthenium(II) under AM 1.5 simulated sunlight.

Mixing and matching: The highly selective detection of chemical-warfare-agent mimics can be achieved by judicious combination of carefully designed fluorescent ligands and metal ions. Designed sensor arrays of these multimetal/multiligand systems represent a modular and versatile approach for the detection of organophosphates and other analytes.

One helps the other: An upstream electrode (1) in a microfluidic channel drives a reaction that produces protons so that the reaction at the downstream electrode (2) becomes thermodynamically or kinetically viable. The shift in redox potential allows the analyte to be detected in conditions in which it would otherwise be undetectable.

Limitations of models in total synthesis are illustrated by a study towards the potent cytotoxic macrolide iejimalide B. Although the Yamaguchi protocol allowed for the esterification of elaborate segments, attempted macrolactonization of the seco acid met with failure (see scheme, Boc= tert-butyloxycarbonyl). The assembly of the seco acid involves some of the most advanced applications of the Julia olefination known to date.

Metathesis to the rescue: Although counterintuitive at first sight, application of ring-closing metathesis (RCM) to a cyclization precursor containing 10 double bonds has led to the selective and high-yielding formation of the macrocyclic core of iejimalide B, a potent cytotoxic agent of marine origin. In contrast, a macrolactonization approach failed to afford this intricate target.

A larger oligomer: Although transition-metal-mediated reactions of alkynes to give dimers, trimers, tetramers, and polymers are well-known, reactions of alkynes to give well-defined oligomers of medium molecular weight (e.g. pentamers, hexamers) are very scarce. The selective hexamerization of HCCPh in the reaction with [OsCl(PCP)(PPh₃)] (PCP=2,6-(Ph₂PCH₂)₂C₆H₃; see scheme) is a rare example thereof.

Radical connection: Organoboranes, prepared in situ from hydroboration of olefins with catecholborane, undergo efficient coupling reactions with vinyl and alkynyl sulfones through a radical mechanism. This procedure was also extended to the acylation and cyanation of organoboranes.

Excellent yields and enantioselectivities can be achieved in the molybdenum–bishydroxamic acid catalyzed asymmetric oxidation of olefins in air at room temperature with an achiral oxidant (see scheme; acac=acetylacetonate). A range of terminal, cis-, and trisubstituted olefins can be used as the substrate. Furthermore, when there are multiple double bonds, the most electron-rich is oxidized.

The long-sought-after palladium-catalyzed coupling of silyl enol ethers, both cyclic and acyclic, with a wide range of aryl bromides and chlorides to form α-aryl ketones is realized. The key to effective activation of the silicon enolate was the use of two metal fluoride additives, which operate in a synergistic fashion.

Without destruction of monocrystallinity: The conformational switching of a dinuclear metal complex between four distinct states (see picture) occurs without destroying the single crystal. This observation implies a substantial degree of cooperativity between host molecules during guest uptake, release, or exchange.

Antitumor agents (−)-acylfulvene and (−)-irofulven are prepared in an approach that employs the powerful enyne ring-closing metathesis reaction to secure the spiro-bicyclic AB rings. Other key features of this synthesis include an efficient aldol-based introduction of the stereocenter at C2, a diazene-mediated reductive allylic transposition, and a ring-closing metathesis/oxidation sequence.

In addition: The chiral Lewis acid mediated radical addition–cyclization–trapping reaction of a hydroxamate ester with two radical acceptors provides a cascade approach for the asymmetric synthesis of various γ-lactams (see scheme; Bn=benzyl, Box=bis(oxazoline), Tf=trifluoromethanesulfonyl).

No longer simply “green” solvents, ionic liquids can be used as backbones to integrate independent components into a multifunctional compound. For example, single-walled carbon nanotubes (SWNTs) are coupled with various anions (X⁻) by a simple anion-exchange reaction (see picture).

Acid advancement: An efficient and highly convergent stereoselective synthesis of pseudotrienic acid B (see structure) has been achieved. Synthetic highlights include a crotyltitanation reaction to control the stereogenic centers at C11 and C20, a cross-metathesis reaction to synthesize the triene moiety, and a Stille cross-coupling reaction to complete the assembly of the carbon framework of the natural product.

Modular design of functional RNAs can be used to tailor molecular properties. Guanosine-rich sequences were introduced as switching devices for functional nucleic acids. TMPyP4 (see picture) was identified as the strongest ribozyme inhibitor known to date. When quadruplex-forming, G-rich sequences were attached to the ribozyme, the TMPyP4-mediated response was inverted from inhibition to activation of the ribozyme reaction.

PtCl₂-catalyzed alkyne activation initiates a domino reaction, in which a heterocyclization is followed by a 1,2-alkyl migration, for the construction of a variety of substituted 3(2H)-furanones. This stereospecific reaction is proposed to proceed through an oxonium ion intermediate (see scheme).

Improving on nature: Azathilones 1 a and 1 b are “non-natural” natural products derived from epothilones through C→N exchange at position 12. They are highly potent inducers of tubulin polymerization (part of a microtubule is shown in the picture) and inhibit human cancer cell growth in vitro. These compounds present a new structural scaffold for microtubule stabilization and are promising lead structures for anticancer-drug discovery.

Available in assorted shapes: Three new oligonuclear complexes self-assemble from tBu-N-diethanolamine and mixtures of iron(II) and iron(III) ions. Depending on the reaction conditions, a compact or linear defective hexacubane, or a body-centered six-sided iron(III) polyhedron (see structure; Fe gold, Ca purple, C gray, N blue, O red, Cl green) is formed.