A Facile Synthesis of α-Phenylchalcogeno(S,Se) α,β-Unsaturated Esters from Ethyl α-Bromo-α-phenylchalcogeno Acetates

Ethyl α-bromo-α-phenylseleno acetate 1 and ethyl α-bromo-α-phenylthio acetate 2 react with aldehydes in the presence of dibutyltelluride to give α-phenylchalcogeno-α,β-unsaturated esters, with Z preferential stereochemistry.     

Centrifugal separation and equilibration dynamics in an electron-antiproton plasma

Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments.     

Raman spectroscopy of pseudomorphic Si0.989C0.011/Si superlattices

Raman spectroscopy is used here to study pseudomorphic Si_0.989C_0.011/Si superlattices grown by molecular beam epitaxy. The high crystalline quality of the samples was tested by a high resolution X-ray diffraction experiment. The lineshape of the LO Si-Si peak shows an asymmetry, which correlates with the increase of the alloy layer width. The Raman spectra show three additional peaks in the high energy side above the LO mode of Si. One of them is due to the local vibration of the C substitutional atoms, and the other two can be attributed to the formation of short range order with C atoms occupying second and third nearest-neighbor places. On the low energy side of the LO Si-Si mode, we have observed two other peaks associated with the relaxation of the Si atoms around the substitutional C. Although the X-ray experiments show clear evidence of superperiodicity, no indication of the superlattice formation could be observed in the parallel polarized Raman spectra, where the folded acoustic modes are allowed.     

Crotofolane‐ and Casbane‐Type Diterpenes from Croton argyrophyllus

Phytochemical analysis of Croton argyrophyllus led to the isolation of five new diterpenes named (5β,6β)‐5,6 : 13,16‐diepoxycrotofola‐4(9),10(18),13,15‐tetraen‐1‐one ( 1 ), (5β,6β)‐5,6 : 13,16‐diepoxy‐2‐epicrotofola‐4(9),10(18),13,15‐tetraen‐1‐one ( 2 ), (5β,6β)‐5,6 : 13,16‐diepoxy‐16‐hydroxy‐2‐epicrotofola‐4(9),10(18),13,15‐tetraen‐1‐one ( 3 ), (5β,6β)‐5,6 : 13,16‐diepoxy‐16‐hydroxy‐2‐epicrotofola‐4(9), 10(18),13,15‐tetraen‐1‐one ( 4 ) and (2E,5β,6E,12E)‐5‐hydroxycasba‐2,6,12‐trien‐4‐one ( 5 ), in addition to the known diterpenes crotonepetin and depressin, and acetylaleuritolic acid and spinasterol. The structures of the isolated compounds were established by a combination of spectroscopic methods, including HR‐ESI‐MS, 2D‐NMR, and X‐ray crystallography.     

Synthesis of Dibromo-Vinyl Chalcogenides

β-Bromovinyl chalcogenides were conveniently prepared in good yields by reacting alkynyl chalcogenides with bromine or by addition of organochalcogenyl bromide to bromoacetylenes in the presence of zinc bromide.     

Catalyst-Dependent Selective Synthesis of O/S- and S/S-Acetals from Enol Ethers

Enol ethers are reacted with mercaptanes to give the corresponding O/S- or S/S-acetals in medium to high yield. Either product can be formed selectively depending on the acid catalyst and the reaction time applied.     

Interaction Study between ESIPT Fluorescent Lipophile-Based Benzazoles and BSA

In this study, the interactions of ESIPT fluorescent lipophile-based benzazoles with bovine serum albumin (BSA) were studied and their binding affinity was evaluated. In phosphate-buffered saline (PBS) solution these compounds produce absorption maxima in the UV region and a main fluorescence emission with a large Stokes shift in the blue–green regions due to a proton transfer process in the excited state. The interactions of the benzazoles with BSA were studied using UV-Vis absorption and steady-state fluorescence spectroscopy. The observed spectral quenching of BSA indicates that these compounds could bind to BSA through a strong binding affinity afforded by a static quenching mechanism (K_q~10¹² L·mol⁻¹·s⁻¹). The docking simulations indicate that compounds 13 and 16 bind closely to Trp134 in domain I, adopting similar binding poses and interactions. On the other hand, compounds 12, 14, 15, and 17 were bound between domains I and III and did not directly interact with Trp134.     

Towards antihydrogen confinement with the ALPHA antihydrogen trap

ALPHA is an international project that has recently begun experimentation at CERN’s Antiproton Decelerator (AD) facility. The primary goal of ALPHA is stable trapping of cold antihydrogen atoms with the ultimate goal of precise spectroscopic comparisons with hydrogen. We discuss the status of the ALPHA project and the prospects for antihydrogen trapping.