Non-destructive Removal of the Bornanesultam Auxiliary in α-Substituted N-Acylbornane-10,2-sultanis under Mild Conditions: An efficient synthesis of enantiomerically pure ketones and aldehydes

α-Substituted N-acylbornane-10, 2 -sultams 6, 9 , and 10 can be converted into enantiomerically pure ketones 5. 13 , and 14 , respectively, via a two-step procedure involving a known mercaptolysis reaction followed by an [Fe(acac)₃]-mediated coupling of the resulting S-benzyl thioesters with Grignard reagents. Furthermore, enantiomerically pure aldehydes 23 can be obtained from α-substituted N-acylbornane-10,2-sultams 6 via a one-step reduction with (i-Bu)₂AIH. No epimerization at the α-chiral center is observed during the cleavage reaction whereby the chiral auxiliary, bornane-10,2-sultam 1 or ent- l , was recovered. By using this methodology, several natural products or precursors thereof can be prepared.     

Symmetrical electron-deficient materials incorporating azaheterocycles

To investigate the potential of di- and tri-azaheterocycles as building blocks for pi-conjugated materials with high electron affinity, linear oligomers incorporating pyrazine and a C(3)-symmetric discotic molecule based on triazine were synthesized. The tridodecyloxyphenyl end-capped ethynylene pyrazinylene oligomers showed remarkable solvatochroism in absorption and emission in solution. The oligomers containing one and two pyrazine rings displayed liquid crystallinity in the solid state. The largest ethynylene pyrazinylene oligomer containing three pyrazine rings had the lowest first reduction potential at -1.08 V. The triazine-derived discotic molecule exhibited UV/Vis and fluorescence behavior comparable to that of the linear oligomers and featured a first reduction potential at -1.49 V, somewhat lower than expected.     

A biosynthetically inspired synthesis of (−)-berkelic acid and analogs

We describe a complete account of our total synthesis and biological evaluation of (?)-berkelic acid and analogs. We delineate a synthetic strategy inspired by a potentially biomimetic union between the natural products spicifernin and pulvilloric acid. After defining optimal parameters, we executed a one-pot silver-mediated in situ dehydration of an isochroman lactol to methyl pulvillorate, the cycloisomerization of a spicifernin-like alkynol to the corresponding exocyclic enol ether, and a subsequent cycloaddition to deliver the tetracyclic core of berkelic acid. Our studies confirm that the original assigned berkelic acid structure is not stable and equilibrates into a mixture of 4 diastereomers, fully characterized by X-ray crystallography. In addition to berkelic acid, C22-epi-berkelic acid, and nor-berkelic acids, we synthesized C26-oxoberkelic acid analogs that were evaluated against human cancer cell lines. In contrast to data reported for natural berkelic acid, our synthetic material and analogs were found to be devoid of activity.     

Observation of Sb2O3 Nanocrystals in SiO2 after Sb Ion Implantation

 Antimony nanocrystals were formed in thin SiO₂ films using low-energy ion implantation of Sb followed by annealing. Using Fourier transform laser microprobe mass spectrometry (FT LMMS), we observed for the first time the presence of antimony oxide in the intermediate phase (as-implanted layer of Sb) by means of signals referring to the intact Sb₂O₃ molecules. Only SbO⁺ fragments, but no adduct ions of Sb₂O₃ could be detected in annealed samples. The size and the distribution of the nanocrystals formed around the initial depth of implantation were studied in the as-implanted samples by high-resolution electron microscopy (HREM). The crystalline structure of these nanocrystals was also studied and the presence of antimony trioxide Sb₂O₃ in the form of valentinite was proven. After the annealing step, the implanted material had spread into a wider band. The method introduced here, based on combining TEM (transmission electron microscopy) and FT LMMS results, offers the possibility of studying the evolution of the phases in Sb nanocrystal formation.     

Silicone oxidation for a‐Si:H passivation of wafers bonded to glass

A possible scenario for wafer‐based silicon photovoltaics is the processing of solar modules starting from thin silicon wafers bonded to glass. However, interactions between the adhesive used for bonding and the solar cell processing can affect the surface passivation of the bonded wafer and decrease cell performances. A method that suppresses these interactions and leads to state‐of‐the‐art a‐Si:H surface passivation is presented in this Letter. The method is based on an increase of the surface cross‐linking of a silicone adhesive by means of an O₂ plasma and it is successfully tested on three different silicones. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Aqueous electrophoretic deposition in asymmetric AC electric fields (AC–EPD)

Electrophoretic deposition (EPD) is a cheap and simple processing technique based on the movement of charged particles in an electrical field (electrophoresis) followed by deposition of these particles on the electrode that attracted them [O. VanderBiest, L.J. Vandeperre, Electrophoretic deposition of materials, Annu. Rev. Mater. Sci. 29 (1999) 327–352]. If not for electrolysis, water would be the solvent of choice instead of the currently commercially used organics. In this work we prove that high voltages can be used for electrophoretic deposition from aqueous suspensions without decomposition of water when applying an asymmetric alternating electric field. The experimental results show that deposits formed using these fields have a green density and surface comparable and even better than those typically obtained using the classic EPD systems. As a result volatile, expensive and environmentally unfriendly solvents are no longer a necessity.     

Chiral polymers by iterative tandem catalysis

Racemic omega-substituted caprolactones can be completely converted into chiral polyesters of remarkable MW and high ee by combining lipase-catalyzed ring-opening polymerization with Ru-catalyzed racemization.     

Efficient luminescence from porous silicon

Photoluminescence measurements are carried out on porous silicon layers. We show the enhancement and stabilization of the luminescence when depositing a silicon nitride layer on top of porous layers.We also demonstrate that direct- and remote-plasma nitridation are good ways to reduce the ageing effect of porous silicon layers due to a passivation of dangling bonds.     

Development of proneurogenic, neuroprotective small molecules

Degeneration of the hippocampus is associated with Alzheimer's disease and occurs very early in the progression of the disease. Current options for treating the cognitive symptoms associated with Alzheimer's are inadequate, giving urgency to the search for novel therapeutic strategies. Pharmacologic agents that safely enhance hippocampal neurogenesis may provide new therapeutic approaches. We discovered the first synthetic molecule, named P7C3, which protects newborn neurons from apoptotic cell death, and thus promotes neurogenesis in mice and rats in the subgranular zone of the hippocampal dentate gyrus, the site of normal neurogenesis in adult mammals. We describe the results of a medicinal chemistry campaign to optimize the potency, toxicity profile, and stability of P7C3. Systematic variation of nearly every position of the lead compound revealed elements conducive toward increases in activity and regions subject to modification. We have discovered compounds that are orally available, nontoxic, stable in mice, rats, and cell culture, and capable of penetrating the blood-brain barrier. The most potent compounds are active at nanomolar concentrations. Finally, we have identified derivatives that may facilitate mode-of-action studies through affinity chromatography or photo-cross-linking.