A Concise and Scalable Strategy for the Total Synthesis of Dictyodendrin B Based on Sequential CH Functionalization

A sequential C? H functionalization strategy for the synthesis of the marine alkaloid dictyodendrin B is reported. Our synthesis begins from commercially available 4‐bromoindole and involves six direct functionalizations around the heteroarene core as part of a gram‐scale strategy towards the natural product.     

Bestimmung der Halogene

Ohne Zusammenfassung     

Miconazole induces fungistasis and increases killing of Candida albicans subjected to photodynamic therapy

Cutaneous and mucocutaneous Candida infections are considered to be important targets for antimicrobial photodynamic therapy (PDT). Clinical application of antimicrobial PDT will require strategies that enhance microbial killing while minimizing damage to host tissue. Increasing the sensitivity of infectious agents to PDT will help achieve this goal. Our previous studies demonstrated that raising the level of oxidative stress in Candida by interfering with fungal respiration increased the efficiency of PDT. Therefore, we sought to identify compounds in clinical use that would augment the oxidative stress caused by PDT by contributing to reactive oxygen species (ROS) formation themselves. Based on the ability of the antifungal miconazole to induce ROS in Candida, we tested several azole antifungals for their ability to augment PDT in vitro. Although miconazole and ketoconazole both stimulated ROS production in Candida albicans, only miconazole enhanced the killing of C. albicans and induced prolonged fungistasis in organisms that survived PDT using the porphyrin TMP-1363 and the phenothiazine methylene blue as photosensitizers. The data suggest that miconazole could be used to increase the efficacy of PDT against C. albicans, and its mechanism of action is likely to be multifactorial.     

Dynamical relativistic effects in photoionization: spin-orbit-resolved angular distributions of xenon 4d photoelectrons near the Cooper minimum

Two decades ago, it was predicted [Y. S. Kim et al., Phys. Rev. Lett. 46, 1326 (1981)] that relativistic effects should alter the dynamics of the photoionization process in the vicinity of Cooper minima. The present experimental and theoretical study of the angular distributions of Xe 4d(3/2) and 4d(5/2) photoelectrons demonstrates this effect for the first time. The results clearly imply that relativistic effects are likely to be important for intermediate- Z atoms at most energies.     

The characteristics and properties of optimised amorphous silicon field effect transistors

A series of experiments aimed at improving the performance of amorphous silicon field effect transistors has been carried out. The dc and dynamic characteristics of the optimised devices are described. Stable devices capable of ON-currents of the order of 100 μA with OFF-currents ?10^?11 A can be fabricated which could, in principle, be used to address more than 1000 lines of a liquid crystal display. The properties of the highly conducting ON-state channel have also been studied. The field effect mobility, 0.3 cm² V^?1 s^?1 at room temperature, has an activation energy of 0.1 eV at the higher gate voltages. The possible reasons for the improvement in performance over earlier devices are discussed.     

Sulfobetaine zwitterionomers based on n‐butyl acrylate and 2‐ethoxyethyl acrylate: Physical properties

New materials with potential applications for adhesives and coatings, based on copolymers containing zwitterionic pendent groups, were investigated. n‐Butyl acrylate and 2‐ethoxyethyl acrylate were copolymerized with a series of five zwitterionic sulfobetaine monomers (SBMs). The structures of the SBMs were varied systematically in terms of (1) intercharge spacing in the zwitterionic moiety and (2) substituent bulkiness at the quaternary ammonium functionality. The effect of varying the sulfobetaine content and structure in the copolymers was investigated, with an emphasis on ion aggregation behavior and physical properties, with dynamic mechanical analysis. The zwitterionomers exhibited the expected biphasic morphology, with the appearance of an ion‐rich glass‐transition temperature. An increase in the storage modulus was observed with increasing SBM content in the rubbery and terminal regions, suggesting an increased degree of ionic crosslinking in the rubbery region and decreased chain mobility in the flow region. Intercharge spacing variation in the sulfobetaine moiety did not have a significant effect on the modulus–temperature curves, contrary to our expectations. Increases in the modulus were much less pronounced for the bulkier SBMs than for the other monomers, possibly because of hindered aggregation of the sulfobetaine moieties. Likewise, matrix polarity had a greater influence on the physical properties of these materials than intercharge separation in the SBMs. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2303–2312, 2002