Readily available phenols can be converted into substituted aryl alkynyl ethers, which react with an N‐oxide as an oxidant and catalytic amounts of a Brønsted acid to provide benzofuranones. If non‐terminal alkynyl ethers are applied, a 1,2‐hydride shift takes place and phenyl acrylates are obtained. Thus activated alkynes can serve as α‐oxy carbene precursors even in the absence of a metal catalyst.

Enantioselective catalysis utilizing G-quadruplex DNA-based artificial metalloenzymes has emerged as a new approach in the field of aqueous-phase homogeneous catalysis. Recently, a catalytic asymmetric Michael addition employing a covalently modified G-quadruplex in combination with Cu ions has been reported. Here we assess, by systematic chemical variation and using various spectrometric techniques, a variety of parameters that govern rate acceleration and stereoselectivity of the reaction, such as the position of modification, the topology of the quadruplex, the nature of the ligand, the length of the linker between ligand and DNA, the chemical identity of monovalent ions and transition metal complexes. The DNA quadruplex modified at position 10 (dU10) with hexynyl-linked bpy ligand showed twice the initial reaction rate as compared with the DNA strand derivatized at position 12 (dU12). The strikingly different dependence of the stereoselectivity on the linker length, and their different spectroscopic properties indicate large differences in the architecture of the catalytic centers between the dU10-derivatized and the dU12-modified quadruplexes. Upon addition of Cu , both types of bpy-derivatized DNA strands form defined 1:1 Cu-DNA complexes stable enough for mass spectrometric analysis, while the underivatized strands exhibit weak and unspecific binding, correlated with much lower catalytic rate acceleration. Both dU10- and dU12-derivatized quadruplexes could be reused ten times without reduction of stereoselectivity.

Aus leicht zugänglichen Phenolen wurden substituierte Aryl‐Alkinyl‐Ether hergestellt, deren Umsetzung mit einem N‐Oxid als Oxidationsmittel in Gegenwart katalytischer Mengen einer Brønsted‐Säure effektiv Benzofuranone ergibt. Nichtterminale Alkinylether durchlaufen dabei eine 1,2‐Hydrid‐Verschiebung, die zu Phenylacrylaten führt. Somit können aktivierte Alkine auch in Abwesenheit von Metallkatalysatoren als α‐Oxycarben‐Vorstufen genutzt werden.

Polyacrylic‐acid‐coated ultra‐small super‐paramagnetic iron oxide nanoparticles were surface‐modified with low‐molecular‐weight sulfobetaines or 3‐(diethylamino)propylamine in order to generate nanoparticles with zwitterionic character (ZW‐NPs). The ZW‐NPs proved highly resistant to serum protein corona formation in vitro, as revealed by atomic force microscopy, SDS‐PAGE and proteomics analysis, and exhibited low cytotoxicity towards A431 and HEK293 cells. The presence of unreacted carboxylic acid groups enabled additional functionalization with fluorescent (Cy5) and radioactive [64Cu–dmptacn; dmptacn=1,4‐bis(2‐pyridinylmethyl)‐1,4,7‐triazacyclononane] moieties. Overall, the ZW‐NPs represent promising platforms for the development of new multimodal diagnostic/therapeutic agents possessing “stealth” properties.

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Guanosine‐rich DNA sequences can fold into quadruplex structures which are not only biologically relevant, but also promising for applications in aqueous homogenous catalysis. Here, an asymmetric Michael addition is catalyzed by covalently modified G‐quadruplexes in combination with copper ions. Using systematic chemical variation and various spectrometric techniques, the key parameters that govern rate acceleration and stereoselectivity were identified. More information can be found in the Full Paper by A. Jäschke et al. on page 12162 ff.