Eines der Haupttoxine bei Fischvergiftungen, das Ciguatoxin (siehe Struktur), war Ziel einer Totalsynthese. Der Syntheseweg beruht auf der Kupplung dreier Segmente, und die Schlüsselumwandlungen umfassen eine Komplexbildung zwischen Acetylen und Dicobalthexacarbonyl.
“My most exciting discovery to date has been that molecules can have a magnetic memory. The biggest challenge facing scientists is to find renewable and sustainable energy sources…?” This and more about Roberta Sessoli can be found on page 2265.
Ring leader : PtCl2 catalyzes intramolecular cyclization of o‐isopropyl or o‐benzyl aryl alkynes to give substituted indene derivatives with good yields and high selectivity. This reaction appears to proceed through an sp3 C? H activation and 1,4‐hydrogen migration pathway (see scheme).
Ordered water : Gypsum has been used for construction for millennia. The structure and water content of calcined gypsum, CaSO4?0.5 H2O, has been under discussion until now: single‐crystal structure analysis (see picture: S yellow, Ca gray, O blue, H red) provides an ordered model that is confirmed by DFT calculations.
Chiral 1,2‐diols have been prepared from α‐aminoxylated aldehydes or cyclohexanone and Grignard reagents with L ‐proline or its tetrazole derivative as the catalyst. The presence of the ate complex of CeCl3?2 LiCl is essential for the high overall yields and good selectivities (see scheme; DMSO=dimethyl sulfoxide, THF=tetrahydrofuran, Tol=tolyl).
Preferred protonation : Does electrospray ionization mass spectrometry produce gas‐phase or liquid‐phase structures? The preferred protonation site in p‐aminobenzoic acid depends upon the medium, and the structure of its conjugate acid varies with the solvent used during spraying.
?My most exciting discovery to date has been always the last one (or better still, the next one). The biggest challenge facing scientists is the responsible use of knowledge and scientific power for the betterment of humanity. …?“ This and more about P. Melchiorre can be found on page 3389.
Nice coat! Organically modified silica (ormosil) is used for the ultrathin nanoprecise coating of individual multiwall carbon nanotubes using a soft‐chemistry approach. The coating layer has a uniform thickness of about 3 nm. The ormosil coating demonstrates the favorable electrical insulating properties of individual multiwall carbon nanotubes.
Conditional cleavage : Photochemical S? N bond cleavage of the Zn2+ complex of N‐dansylcyclen (ZnL2) in aqueous solution was investigated. Moreover, photolysis of ZnL2 (see scheme) facilitated photoreversion of cis,syn‐thymine photodimer (T[c,s]T).
Sleeping beauty? Is the scientific community about to kiss awake iron catalysis, a topic that has been dormant for decades? A recent study on a user‐friendly direct cross‐coupling reaction of alkyl and aryl halides constitutes an important step toward this end through the integration of two different iron‐catalyzed elementary steps into a practical one‐pot procedure.
Bonded or not bonded? An ab initio valence bond study of [1.1.1]propellane shows that the two bridgehead carbons are linked by a strong and direct σ bond that is neither classically covalent nor classically ionic, but rather a charge‐shift bond, in which the covalent–ionic resonance energy plays the major role. As such, the central bond of [1.1.1]propellane closely resembles the single bond of difluorine.
Funky discotics : Photoconductivity is measured in newly synthesized cyclopalladated metallomesogens exhibiting hexagonal columnar mesophases at room temperature. The tuning of the HOMO/LUMO energy levels by modification of the chain/core linkage (ester 1 vs ether 2 ) makes compound 2 photoconductive across the whole UV/Vis/NIR range.
Inorganic enzyme? Ceria nanoparticles exhibit unique oxidase‐like activity at acidic pH values. These redox catalysts can be used in immunoassays (ELISA) when modified with targeting ligands (see picture; light blue and yellow structures are nanoparticles with attached ligands). This modification allows both for binding and for detection by the catalytic oxidation of sensitive colorimetric dyes (e.g. TMB).
Ringing the changes : The total synthesis of the title compound centers around a novel strategy that employs a nickel(0)–phosphine complex and triethyl borane in an efficient closure of a 14‐membered ring through C? C bond formation (see scheme; cod=cyclooctadiene). The synthesis was accomplished in 10 steps and in approximately 9 % overall yield.
Playing the sax : The enantioselective total syntheses of (?)‐ and (+)‐decarbamoyloxysaxitoxin (doSTX) and (+)‐saxitoxin (STX) are reported. A new methodology was developed for the synthesis of STXs, featuring discriminative reduction of the nitro group and N? O bond in nitroisoxazolidine.
