Indium-mediated reduction of hydroxylamines to amines

[reaction: see text] A novel and simple procedure for reduction of hydroxylamines to the corresponding amines by means of indium powder in aqueous media is reported. Applicability to one-pot reactions and isoxazolidine N-O bond reduction is also demonstrated. A catalytic version of the process using 2-5% In in the presence of other metals (Zn, Al) has been successfully developed.     

Antiparasite and antimycobacterial activity of passifloricin analogues

Several structural analogues of the polyketide passifloricin lactone were synthesized using asymmetric stereoselective allylations and ring-closing methateses as key reactions. These compounds were active in vitro against intracellular amastigotes of Leishmania panamensis (strain UA140), trophozoites of Plasmodium falciparum (strain NF54), and Mycobacterium tuberculosis (strain H₃₇Rv). However, in spite of the significative antiparasitic activity of some synthetic analogues a high cytotoxicity was also observed. Based on these results a lactam derivative was also synthesized. This compound maintained a good level of activity with less toxicity.     

Low-spin states in <Superscript>182</Superscript>Os and K<Superscript>π</Superscript> = 0<Superscript>+</Superscript>, 2<Superscript>+</Superscript> excited bands

Excited states in ¹⁸²Os were populated by the β⁺/EC decay of ¹⁸²Ir following mass separation. Gamma-ray and conversion electron spectroscopy techniques were employed. Monopole (E0) contributions were determined in transitions populating the ground-state band. A systematic study of the low-spin structures in the Os isotopes is presented and a detailed analysis in the framework of a microscopic configuration mixing approach is performed.     

Heptapeptide mimic of ohmefentanyl binding in the discontinuous mu-opiod receptor

[reaction: see text] Ohmefentanyl binds to the rat mu-opiod receptor via two dipeptide sequences (Trp-His and Asp-Tyr) that are separated by 170 residues. A turn-inducing tripeptide, Pro-Aib-Aib, holds the dipeptides in a conformation that binds the narcotic (K(b) = 7.1 x 10(4) M(-)(1)) in THF. Binding is specific for ohmefentanyl over morphine and is accompanied by a conformational change in the heptapeptide host. Control experiments with a Gly-Gly-Gly tripeptide linking the dipeptides show no evidence of binding.     

A new application of the diamond anvil cell: Measurements under uniaxial stress

We present optical absorption measurements on thin films of CuCl and CuBr at 100K under uniaxial stress up to ～3.0 GPa. The thin films were prepared by evaporating onto the inner face of one diamond of a diamond anvil cell. From the splitting of the excitons we were able to determine the shear deformation potential d = -0.69 ± 0.03 eV for CuBr and d = +0.45 ± 0.08 eV for CuCl. Our measurements indicate also that the spin-orbit splitting increases in both materials with increasing pressure. A new shear-induced phase is found for CuCl above 4.8 GPa.     

Relative Raman cross sections and deformation potentials of several semiconductors at the E1 resonance

The relative cross sections for one-phonon scattering at the E₁ resonance have been measured for several cubic semiconductors. Using the dielectric theory of the Raman tensor and the values of the real and imaginary parts of the dielectric constant determined from optical measurements we are able to obtain relative values for the intraband deformation potential of the valence bands d⁵_3,0. Taking d⁵_3,0 = 1 for Ge we find the values 2.4, 1.0, 0.42, 0.64 and 1.1 for Si, GaAs, Mg₂Si, Mg₂Ge, and Mg₂Sn, respectively.     

Polymerisation von Styrol mit Trifluormethansulfons?ure. Leitf?higkeit, Spektroskopie und kinetische Messungen

Ohne Zusammenfassung     

Resonant Raman scattering in germanium and zincblende-type semiconductors temperature dependence

We have measured the resonance in the Raman scattering near the E₁ gaps of InAs and of a Ge_0.77 Si_0.23 alloy at 77, 300 and 594°K. In contrast to the E₁ gap determined in absorption and transmission measurements, the coresponding peak in the spectral dependence of the scattering cross section shifts very little with temperature; it occurs at all temperatures very near the energy of the absorption peak measured at low temperatures (∼ 77°K).     

Elastic constants and Raman frequencies of heavily doped Si under uniaxial stress

It is shown that the effects of doping on the $\text{C}{}_{\mathrm{<mtext>44</mtext>}}$ elastic constant and on the Raman frequency of p-type silicon disappear upon application of a stress along [001], with a very similar functional dependence on stress. These experiments prove the intimate relationship between these two phenomena and the degeneracy of the valence bands of silicon.