Stable carbocations. Part 21. Intra-ionic proton transfer in electrophilic cyclisation of 3-ferrocenyl-1-phenylpropen-1-yl cation

The spontaneous conversion of the title cation into the 1-phenyl[3](1,2) ferrocenophan-1-yl cation proceed by intra-ionic 1, 3-shift of a cyclopentadienyl α-ring proton to C(2) of the homoannular bridge; the letter cation undergoes deprotonation by stereospecific loss of the exo-proton adjacent to C⁺.     

Atomic absorption inhibition titration of orthophosphate and polyphosphates

The atomic absorption inhibition titration of phosphates was studied for two types of burner. Dependence on gas Flow-rates was observed. The method with a pre-mix burner was employed to determine phosphate in surface and waste waters. The results are compared with those by the standard method. The proposed method was found to be rapid, simple and accurate.     

Potent and selective structure-based dibenzofuran inhibitors of transthyretin amyloidogenesis: kinetic stabilization of the native state

Transthyretin (TTR) amyloidogenesis requires rate-limiting tetramer dissociation and partial monomer denaturation to produce a misassembly competent species. This process has been followed by turbidity to identify transthyretin amyloidogenesis inhibitors including dibenzofuran-4,6-dicarboxylic acid (1). An X-ray cocrystal structure of TTR.1(2) reveals that it only utilizes the outer portion of the two thyroxine binding pockets to bind to and inhibit TTR amyloidogenesis. Herein, structure-based design was employed to append aryl substituents at C1 of the dibenzofuran ring to complement the unused inner portion of the thyroxine binding pockets. Twenty-eight amyloidogenesis inhibitors of increased potency and dramatically increased plasma TTR binding selectivity resulted. These function by imposing kinetic stabilization on the native tetrameric structure of TTR, creating a barrier that is insurmountable under physiological conditions. Since kinetic stabilization of the TTR native state by interallelic trans suppression is known to ameliorate disease, there is reason to be optimistic that the dibenzofuran-based inhibitors will do the same. Preventing the onset of amyloidogenesis is the most conservative strategy to intervene clinically, as it remains unclear which of the TTR misassembly intermediates results in toxicity. The exceptional binding selectivity enables these inhibitors to occupy the thyroxine binding site(s) in a complex biological fluid such as blood plasma, required for inhibition of amyloidogenesis in humans. It is now established that the dibenzofuran-based amyloidogenesis inhibitors have high selectivity, affinity, and efficacy and are thus excellent candidates for further pharmacologic evaluation.     

Comparison of the growth and degradation of poly(glycolic acid) and poly(ε‐caprolactone) brushes

The growth and degradation of poly(glycolic acid) (PGA) and poly(ε‐caprolactone) (PCL) brushes were compared. Using tin (octanoate) as the catalyst, optimal conditions were found for growth of each polyester brush from the hydroxy‐terminated silicon surface via ring‐opening polymerization. PCL brushes grew thicker at elevated temperatures but the thickest PGA brushes grew at room temperature. Unlike bulk polyesters that can degrade under both acidic and basic conditions, the confined surface polyester brushes only degraded under neutral or basic conditions. The degradation mechanism of grafted polyester brushes was probed through a blocking test. It was shown that the terminal hydroxy groups of these polyester brushes were essential to the degradation process indicating a preferential backbiting mechanism. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4643–4649     

Analysis of the results of calibrating meteoritic olivine crystals with238U nuclei at the Bevalac accelerator

The results are presented of calibrating the sensitivity of olivine crystals from meteorites by the²³⁸U nuclei produced at the Bevalac accelerator. The comparative studies of the spectra of the etchable track lengths due to the²³⁸U nuclei and to fossil tracks in these olivines have shown that the group of the 210 m fossil tracks observed in 1980 at the LNR, JINR is due to the galactic cosmic-ray nuclei of the Th-U group. As regards the origin of the 340–360 m group of fossil tracks which were considered in [2] to be candidates for superheavy nuclei in cosmic rays the presence of the track with a length of up to 360 m in the calibrating²³⁸U track length spectra indicates that the above interpretation has to be questioned. The possible ways of the unambiguous identification of the group of the abnormally long fossil tracks are discussed.In conclusion the authors express their deep gratitude to Academician G.N. Flerov for thoughtful guidance and permanent attention to this study. The authors wish to thank Dr. G.M. Ter-Akopian for very useful discussions and advice and also for his help during the calibrations on Bevalac, Dr. R.I. Petrova for her help in preparing olivine crystal mounts and for their subsequent annealing and etching, and Mrs. G.G. Bankova and G.P. Knyazeva for the thorough microscopic measurements of the²³⁸U track spectra.