Selective modifications of hydrophobic vitamin B12 derivatives at c-and d-positions

The acid-sensitivity of vitamin B(12) derived mono- and diamides was studied. It was found that the use of reductive ring-opening of the lactone moiety deactivated undesired decomposition of c-mono- and c,d-diamides under acidic conditions. As a result, reactions gave respectively c- or d-acids which were further functionalized via coupling with amino acids. Though mono- and diamides exhibited acid sensitivity, they were used for the preparation of several highly functionalized molecules showing their stability under various reaction conditions.     

On the calculations of interaction energies and induced electric properties within the polarizable continuum model

In this work we investigate the influence of a polarizable environment on the interaction energies and the interaction-induced (excess) static electric dipole properties for the selected model hydrogen-bonded complexes. The excess properties were estimated for water and hydrogen fluoride dimers using the supermolecular approach and assuming the polarizable continuum model (PCM) as a representation of the polarizable environment. We analyze in this context the performance of the counterpoise correction and the consequences of various possible monomer cavity choices. The polarizable environment reduces the absolute magnitudes of interaction energies and interaction-induced dipole moments, whereas an increase is observed for the absolute magnitudes of induced polarizabilities and first hyperpolarizabilities. Our results indicate that the use of either monomeric (MC) or dimeric (DC) cavities in calculations of monomer properties does not change qualitatively the resultant excess properties. We conclude that the DC scheme is more consistent with the definition of the interaction energy and consequently also the interaction-induced property, whereas the MC scheme corresponds to the definition of stabilization energy. Our results indicate also a good performance of the counterpoise correction scheme for the self-consistent methods in the case of all studied properties.     

Ramsey’s theorem for colors from a metric space

The Ramsey theorem says that for any countably infinite undirected clique whose edges are colored by a finite number of colors, there is an infinite subclique whose edges are colored by a single color. In this note, we generalize the theorem to a situation where the colors form a compact metric space.     

Cavity ring down spectroscopy: detection of trace amounts of substance

We describe several applications of cavity ring-down spectroscopy (CRDS) for trace matter detection. NO₂ sensor was constructed in our team using this technique and blue-violet lasers (395–440 nm). Its sensitivity is better than single ppb. CRDS at 627 nm was used for detection of NO₃. Successful monitoring of N₂O in air requires high precision mid-infrared spectroscopy. These sensors might be used for atmospheric purity monitoring as well as for explosives detection. Here, the spectroscopy on sharp vibronic molecular resonances is performed. Therefore the single mode lasers which can be tuned to selected molecular lines are used. Similarly, the spectroscopy at 936 nm was used for sensitive water vapour detection. The opportunity of construction of H₂O sensor reaching the sensitivity about 10 ppb is also discussed.     

Bromine adsorption on Ge(001) surface: comparative study for coverages of 0.25, 0.5, 0.75 and 1 monolayer

We present theoretical analysis of bromine adsorption on the Ge(001)-p(1×2) surface. Bromine adsorbs dissociatively at the Ge(001) surface and the adlayer of bromine develops ordered structures of adatoms bound to substrate dimers. We analyse atomic configurations of the Ge(001) surface covered by 0.25, 0.5, 0.75 and 1 monolayer of bromine. Various stable surface structures, found in calculations, are presented and their energies are compared. Simulated STM images are also discussed for the considered configurations.      

Weak radiative decays of the B meson and bounds on $$M_{H^\pm }$$ in the Two-Higgs-Doublet Model

In a recent publication (Abdesselam et al. arXiv:1608.02344), the Belle collaboration updated their analysis of the inclusive weak radiative B-meson decay, including the full dataset of \((772 \pm 11)\times 10^6~B\bar{B}\) pairs. Their result for the branching ratio is now below the Standard Model prediction (Misiak et al. Phys Rev Lett 114:221801, 2015, Czakon et al. JHEP 1504:168, 2015), though it remains consistent with it. However, bounds on the charged Higgs boson mass in the Two-Higgs-Doublet Model get affected in a significant manner. In the so-called Model II, the 95% C.L. lower bound on \(M_{H^\pm }\) is now in the 570–800 GeV range, depending quite sensitively on the method applied for its determination. Our present note is devoted to presenting and discussing the updated bounds, as well as to clarifying several ambiguities that one might encounter in evaluating them. One of such ambiguities stems from the photon energy cutoff choice, which deserves re-consideration in view of the improved experimental accuracy.     

Reaction of 5,5-diphenyl-2-thiohydantoin with 1,3-dibromopropane under phase transfer catalytic conditions : Crystal and molecular structure of 2,3,4,5-tetrahydro-7,7-diphenylimidazo-[2,1-b]-thiazine -6(7H)-one

The reaction of the potassium salt of 5,5-diphenyl-2-thiohydantoin with 1,3-dibromopropane and triethylamine carried out under phase transfer catalytic conditions gave almost quantitatively two isomeric diphenylimidazothiazine 2 and 3 in a ratio ca 1:2. 2,3,4,5-Tetrahydro-7,7-diphenylimidazo- [2,1-b]-thiazine-6(7H)-one (3) crystallises from DMSO in the space group P2₁2₁2₁ with a = 8.488(3), b = 11.682(4), c = 15.522(5)Å. The 6-membered thiazine ring in 3 adopts a sofa conformation.     

Acyclic and cyclic aminophosphonic acids: asymmetric syntheses mediated by chiral sulfinyl auxiliary

Aminophosphonic acids have become increasingly important in different fields of chemistry, medicine and agriculture. This account outlines the results obtained in the author’s laboratory on the asymmetric synthesis of acyclic and cyclic aminophosphonic acids mediated by chiral sulfinyl auxiliary. A key reaction in the synthesis of enantiopure α- and β-aminoalkanephosphonic acids involving a highly diastereoselective addition of phosphite anions or α-phosphonate carbanions to enantiopure sulfinimines is discussed. The asymmetric cyclopropanation of enantiopure α-phosphorylvinyl sulfoxides with sulfur ylides is presented as a platform for developing a new approach to optically active β-aminocyclopropanephosphonic acids. It is exemplified by the total synthesis of enantiopure β-amino-γ-phenylcyclopropanephosphonic acid - a constrained analogue of the GABA_B antagonist phaclofen.     

Vibrational circular dichroism and absolute configuration of chiral sulfoxides: tert-butyl methyl sulfoxide

Mid-infrared vibrational unpolarised absorption and vibrational circular dichroism (VCD) spectra of CCl4 solutions of tert-butyl methyl sulfoxide (1) are reported. The spectra are compared to ab initio density functional theory (DFT) calculations carried out using two functionals, B3PW91 and B3LYP, and two basis sets, 6-31G* and TZ2P. The VCD spectra are calculated using Gauge-invariant atomic orbitals (GIAOs). The analysis of the VCD spectrum confirms the R(-)/S(+) absolute configuration of 1. The advantages and disadvantages of VCD spectroscopy in determining the absolute configurations of chiral sulfoxides are discussed.     

A metrizable X with Cp(X) not homeomorphic to Cp(X) × Cp(X)

We give an example of an infinite metrizable space X such that the space C_p(X), of continuous real-valued functions on X endowed with the pointwise topology, is not homeomorphic to its own square C_p(X) × C_p(X). The space X is a zero-dimensional subspace of the real line. Our result answers a long-standing open question in the theory of function spaces posed by A. V. Arhangel’skii.