Enantioselective synthesis of functionalized γ-butyrolactones

Sharpless asymmetric dihydroxylation and aminohydroxylation of (E)-dimethyl-2-alkylidene glutarates 2 were shown to afford enantio-enriched or enantiopure highly functionalized γ-butyrolactones 3 and 7.     

Fullerohelicates: a new class of fullerene-containing supermolecules

A multicomponent array made of a bis-copper(I) helicate core and two peripheral fullerene subunits has been prepared and electron transfer from the photoexcited Cu(I)-complexed unit to C60 occurs.     

Radical amination with sulfonyl azides: a powerful method for the formation of C-N bonds

A novel reaction for the introduction of an azide moiety by means of a mild radical process is currently under development. Sulfonyl azides are suitable azidating agents for nucleophilic radicals, such as secondary and tertiary alkyl radicals. More electrophilic radicals, such as enolate radicals, do not react with sulfonyl azides. This feature allowed the development of efficient intra- and intermolecular carboazidations of olefins. Due to the versatility of the azido group, this reaction has an important synthetic potential, as already demonstrated by the preparation of the core of several alkaloids, particularly those containing an amino-substituted quaternary carbon center, such as FR901483.     

Octasubstituted metal-free phthalocyanine as core of phosphorus dendrimers: a probe for the properties of the internal structure

The synthesis of a new family of phosphorus dendrimers built from an octasubstituted metal-free phthalocyanine core is described up to generation 5. This core is used as a sensor and a probe for analyzing the properties of the internal structure and the influence of each structural part (core, branches, surface) upon the whole structure. UV-visible spectra show both a hyperchromic and bathochromic effect on the Q-bands with increasing generation, indicating that the chromophore is more isolated, and that the dendritic shell mimics a highly polar solvent. There is no evidence for aggregation, except for generation 0, showing again the isolation of the core. However, the dendritic shell is permeable to aqueous acids and bases, as demonstrated by the reversible splitting of the Q-band in an acidic medium (neutral form of the phthalocyanine) and the single Q-band in a basic medium (dianionic form), even for generation 4. The fluorescence quantum yield for the neutral form increases with increasing generation. The dianionic form of generation 0 is poorly fluorescent, whereas generations 3 and 4 (G3 and G4) exhibit better fluorescence. The cores of G3 and G4 are highly sensitive optical sensors for H3O+ and OH-. These experiments are carried out in THF/water mixtures, and the influence of water on the structure has been checked. The hydrodynamic radius of generation 4 is measured by NMR diffusion (pulse gradient spin-echo) experiments. R(H) varies from 35.4 A at 4 mol % of water to 32.5 A at 64 mol % of water in THF, indicating the hydrophobic nature of these dendrimers.     

Dimethyl Sulfoxide: A Bio-Friendly or Bio-Hazard Chemical? The Effect of DMSO in Human Fibroblast-like Synoviocytes

The effect of dimethyl sulfoxide (DMSO) in rheumatoid arthritis (RA) human fibroblast-like synoviocytes (FLSs) has been studied on five different samples harvested from the joints (fingers, hands and pelvis) of five women with RA. At high concentrations (>5%), the presence of DMSO induces the cleavage of caspase-3 and PARP-1, two phenomena associated with the cell death mechanism. Even at a 0.5% concentration of DMSO, MTT assays show a strong toxicity after 24 h exposure (≈25% cell death). Therefore, to ensure a minimum impact of DMSO on RA FLSs, our study shows that the concentration of DMSO has to be below 0.05% to be considered safe.     

ToF-S-SIMS molecular 3D analysis of micro-objects as an alternative to ion beam erosion at large depth: application to single inkjet dots

Molecular depth profiling is needed to develop high-tech materials optimised to the μm or even up to the nm scale. Recent progress in time-of-flight static secondary ion mass spectrometry (ToF-S-SIMS) offers perspectives to molecular depth profiling. However, at this moment, the methodology is not yet capable to deal with a range of materials science applications because of the limited depth range, the loss of intensity in the subsurface and the loss of depth resolution at large distances from the original surface. Therefore, the purpose of this paper is to develop a complementary approach for the molecular 3D analysis at large depth, using a combination of ultra-low angle microtomy (ULAM) and surface analysis of the sectioned material with ToF-S-SIMS. Single inkjet dots with a diameter of 100 μm and height of 22 μm on a PET substrate have been used as a test system for the methodology. It is demonstrated that the use of a diamond knife allows the molecular composition and distribution of components within the microscopic feature to be probed with a lateral resolution of 300 nm. Hence the methodology approaches the physical limit for ion imaging of organic components with local concentrations in the % range. In practice, the achievable depth resolution with ULAM-S-SIMS is ultimately limited by the surface roughness of the section. Careful optimisation of the ULAM step has resulted in a surface roughness within 6 nm (R _a value) at a depth of 21 μm. This offers perspective to achieve 3D analysis with a depth resolution as good as 18 nm at such a large distance from the surface. Furthermore, the ULAM-S-SIMS approach is applicable to materials unamenable to ion beam erosion. However, the method is limited to dealing with, for instance, Si or glass substrates that cannot be sectioned with a microtomy knife. Furthermore, sufficient adhesion between stacked layers or between the coating and substrate is required. However, it is found that the approach is applicable to a wide variety of industrially important (multi)layers of polymers on a polymer substrate.     

Synthesis of Aminopyridines and Aminopyridones by Cobalt‐Catalyzed [2+2+2] Cycloadditions Involving Yne‐Ynamides: Scope,Limitations, and Mechanistic Insights

An in‐depth study of the cobalt‐catalyzed [2+2+2] cycloaddition between yne‐ynamides and nitriles to afford aminopyridines has been carried out. About 30 nitriles exhibiting a broad range of steric demand and electronic properties have been evaluated, some of which open new perspectives in metal‐catalyzed arene formation. In particular, the use of [CpCo(CO)(dmfu)] (dmfu=dimethyl fumarate) as a precatalyst made possible the incorporation of electron‐deficient nitriles into the pyridine core. Modification of the substitution pattern at the yne‐ynamide allows the regioselectivity to be switched toward 3‐ or 4‐aminopyridines. Application of this synthetic methodology to the construction of the aminopyridone framework using a yne‐ynamide and an isocyanate was also briefly examined. DFT computations suggest that 3‐aminopyridines are formed by formal [4+2] cycloaddition between the nitrile and the intermediate cobaltacyclopentadiene, whereas 4‐aminopyridines arise from an insertion pathway.