Perfluoro‐Tagged Benzyloxycarbonyl Protecting Group and Its Application in Fluorous Biphasic Systems

The synthesis of a new perfluoro‐tagged benzyloxycarbonyl protecting group is reported, as well as its application in the parallel protection of amines. Isolation of the protected amines was performed by simple liquid‐liquid extraction between perfluorinated and organic solvents. Deprotection was achieved by standard hydrogenolysis. The novel protecting group was also applied to cyclization protocols leading to quinazoline‐2,4‐diones. These products were isolated by simple extraction procedures     

Embedded-ring migration on graphene zigzag edge

Reaction pathways are presented for hydrogen-mediated isomerization of a zigzag graphene edge containing a five-member carbon ring surrounded by six-member rings. A new reaction sequence in which this embedded five-member ring moves, or migrates, through the edge has been identified. The elementary steps of the pathways were analyzed using density functional theory (DFT). Rate coefficients were obtained by classical transition state theory utilizing the DFT energies, frequencies, and geometries. The results indicate that this new reaction sequence is competitive with the other important zigzag edge reactions allowing embedded five-member rings to move freely within a zigzag edge. The embedded rings have slight thermodynamic preference for the interior of the edge over the corner for large substrates.     

Numerical Simulations of Arterial Walls Based on IVUS-Data

Atherosclerosis has become one of the most frequent causes of death in the last decades. So the analysis and improvement of corresponding medical treatments, e.g., balloon-angioplasty or stenting, are significant tasks in the fields of biomechanics and biomedical engineering. One important component of the simulation of arterial walls, especially of atherosclerotically degenerated ones, is the knowledge of their anatomical and physiological composition. The intravascular ultrasound and the interpretation by the Virtual Histology provide cross-sectional images of the diseased arterial walls where the different components are characterized by color-coding. The topic of this contribution is the 3D reconstruction and discretization of the artery using these color-coded images and the biplane angiography. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Methyl 4-toluenesulfonyloxymethylphosphonate, a new and versatile reagent for the convenient synthesis of phosphonate-containing compounds

A straightforward procedure leading to the new phosphonylating reagent, methyl 4-toluenesulfonyloxymethylphosphonate, requiring no chromatographic purification is described. This stable reagent works with the same efficiency as dimethyl and other dialkyl esters for the introduction of an O-phosphonomethyl moiety while, in contrast to dimethyl ester, it does not cause any unwanted methylation of sensitive functionalities. Its utility for the alkylation of protected nucleosides in high yield is exemplified.     

Oxidative Addition Reactions of Element–Hydrogen Bonds with Different Polarities to a Gallium(I) Compound

The gallium(I) derivative [Ga({N(dipp)CMe}₂CH)] ( 1 ; dipp=2,6‐diisopropylphenyl) undergoes facile oxidative addition reactions with various element–hydrogen bonds including N? H, P? H, O? H, Sn? H, and H? H bonds. This was demonstrated by its reaction with triphenyltin hydride, ethanol, water, diethylamine, diphenylphosphane, and dihydrogen. All products were characterized by means of single‐crystal X‐ray structure determination, NMR spectroscopy, IR spectroscopy, and mass spectrometry.     

Photoisomerisation in single molecules of nitroprusside embedded in mesopores of xerogels

Photoswitchable hybrid materials are successfully prepared by embedding guanidinium nitroprussides (GuNP, (CN₃H₆)₂[Fe(CN)₅NO]) into mesopores of transparent xerogel monoliths. The such prepared hybrid materials exhibit a higher photostability than the corresponding GuNP solutions, whereby the chemical stability of the [Fe(CN)₅NO]²⁻-anion in titania gel is nearly infinite. By irradiation with light in the blue-green spectral range one nitrosyl isomer is formed by a 180° rotation of the NO ligand changing the Fe–NO into a Fe–ON coordination (SI), which is detected by the shift of the ν(NO) stretching vibration from 1945 cm⁻¹ (Fe–NO) to 1820  cm⁻¹ (Fe–ON). Consequently there is enough space around the NO-ligand for such movement in xerogel mesopores. The embedding in silica xerogels increases the achievable population of the isomeric nitrosyl configuration to about 15% with respect to a single crystalline powder where only 9% are reached.     

Mechanistic Insight into Formation of Oxo‐Iron(IV) Porphyrin π‐Cation Radicals from Enzyme Mimics of Cytochrome P450 in Organic Solvents

Two new models for cytochrome P450 in which the thiolate axial ligand is replaced by an RSO₃^? group, form oxo‐iron(IV) porphyrin π‐cation radicals as sole oxidation products in “peroxo shunt” reactions (see scheme) independent of the nature of the employed solvent (polar or non‐polar) and electronic nature of the porphyrin rings.

     

Pentagerma[1.1.1]propellane: A Combined Experimental and Quantum Chemical Study on the Nature of the Interactions between the Bridgehead Atoms

Ge, whiz! A detailed study of the synthesis, structure, redox chemistry, and bonding properties of pentagerma[1.1.1]propellane ( 1 , see picture) examines fundamental aspects of the interactions between the bridgehead germanium atoms. DFT and CASSCF calculations unravel the biradicaloid characteristics of 1 , and preliminary reactivity studies indicate that 1 features some radical‐type behavior.

     

Asymmetric flow field‐flow fractionation of liposomes: 2. Concentration detection and adsorptive loss phenomena

The applicability of different concentration detection methods for online quantification of liposomes upon asymmetric flow field‐flow fractionation was investigated. Filter‐extruded egg phosphatidylcholine liposomes of different size were used. Online quantification using a differential refractive index (dRI) detector was found feasible for relatively high sample loads in the magnitude of 100 μg lipid (under the chosen fractionation conditions). UV–Vis detection of the turbidity of liposomes was ruled out as online detection method because turbidity increases with particle size and the signal is not only concentration but also particle‐size dependent. Staining of liposomes by Rhodamine phosphatidylethanolamine or Sudan Red and subsequent online UV–Vis detection at the absorption maximum of the dye enabled quantification with much higher sensitivity than dRI detection. Furthermore analyte loss and carry‐over phenomena upon repeated injection of varying liposome sample loads were studied using regenerated cellulose (RC) membranes as accumulation wall. It could be shown that RC membranes are prone to adsorption in case of very small sample loads (0.5 μg). This effect may be overcome by pre‐saturation of the membrane with sample loads of at least 2 μg. For higher sample loads adsorptive losses play a minor role. Recovery from pre‐saturated membranes reached approximately 100% and carry‐over was found negligible.