Attraktives Chlor : Nichtkovalente Wechselwirkungen zwischen Chlor‐ oder Brom‐Atomen und aromatischen Ringen in Proteinen bieten einen neuen Ansatzpunkt für die Beeinflussung der molekularen Erkennung. Die Einführung dieser Substituenten an spezifischen Positionen zweier Faktor‐Xa‐Inhibitoren erhöht deren freie Bindungsenergie durch die Wechselwirkung mit einer Tyrosineinheit. Das allgemeine Vorkommen dieses Strukturmotivs wird anhand zahlreicher Kristallstukturen und quantenchemischer Rechnungen belegt (siehe Bild).
Excellent couplings : Recent developments in the metal‐catalyzed C? H activation of sp3 centers in an α position relative to an amine nitrogen atom are presented. Their reaction with alkenes to give alkylamines (hydroaminoalkylation) is also summarized (see general scheme).
“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.
Taking shortcuts : A remarkably short and high‐yielding asymmetric total synthesis of (?)‐oseltamivir takes advantage of organocatalysis and single‐pot domino operations. The target, known as the drug Tamiflu, is prepared efficiently in a short time, and also its derivatives can be synthesized effectively.
A stereocontrolled total synthesis of the cytotoxic spiroacetal‐containing polyketide (?)‐spirangien A is described. This utilizes an aldol‐based strategy to construct a common stereotetrad intermediate that was elaborated into the spiroacetal core, followed by the introduction of the unstable pentaene‐containing side chain, performed with exclusion of light, using sequential Stille cross‐coupling reactions.
Collisional activation demonstrates that the stable ions from o-nitrobenzaldehydedimethylacetale possess the structure of ionized o-nitroso benzoic acid methyl ester. Contrary to previous conclusions it is demonstrated that the structure of the stable ions (m/e 135) from different precursors [i.e. o-nitrobenzyl alcohol o-nitrobenzyl cyanide and o-nitrobenzaldoxime is best represented by 2,1-benzisoxazoline-3-one. Ionized o-nitrosobenzaldehtde rearranged to 2,1-benzisoxazoline-3-one prior to collision induced decomposition, whereas 2-benzoxazolinone and 3-hydroxy-1,2-benzisoxazole do not rearrange within 10?5 s. 相似文献
A variety of tertiary silanes , even those with functional substituents, undergo an unprecedented iron‐catalyzed dehydrogenative coupling (see scheme) in a convenient approach to disilanes, including unsymmetrical disilanes and polymers with Si? Si bonds in the backbone. Consideration of the catalytic reaction pathway revealed the intermediacy of a hydrido(disilyl)iron(IV) complex.
As simple as it gets! Potassium tert‐butoxide alone catalyzes the direct dehydrogenative Si? O coupling of several synthetically important silanes with 1°, 2°, and even 3° alcohols without the need for stoichiometric hydrochloric acid scavengers. The stereoretentive mechanism is probed with a silicon‐stereogenic silane.
A light touch is all that is required to cleave a maleimide C? N bond to effect a [5+2] photocycloaddition with a sterically encumbered C?N moiety (see scheme).
Discriminating elimination : A new method for the synthesis of methyl‐branched trisubstituted Z olefins, a structural motif in many polyketides with anticancer activity, relies on an ?OH‐induced decarboxylative Grob‐type fragmentation (see scheme; Ms=mesyl). The starting materials are β‐mesyloxy lactones with a quaternary α center, which are prepared by aldol reactions in a diastereo‐ and enantioselective manner.
Mark us bent! The synthesis, structure, and single‐ and two‐photon spectroscopic properties of a series of pyrimidine‐based (bent‐shaped) molecules are reported. These allow structure‐property relationships and guidelines for both the development and application of TPA compounds to be derived.
A different drummer : The existence of endohedral germanium clusters was predicted earlier by gas‐phase experiments. The [Co@Ge10]3? anion now synthesized is surprising, as it breaks with a long line of exclusively deltahedral structures found in the past. Instead, it has a regular pentagonal‐prismatic structure (see picture; Co gray, Ge red).
“My first experiment was the Wittig reaction to prepare chiral allenes. If I wasn′t a scientist, I would be a historian. …?” This and more about Yoshiaki Nishibayashi can be found on page 4276.