Asymmetric addition of a nitrogen nucleophile to an enoate in the presence of a chiral phase‐transfer catalyst: A novel approach toward enantiomerically enriched protected β‐amino acids

A proof of concept for the asymmetric organocatalytic aza‐Michael addition reaction of nitrogen nucleophiles with simple and readily available alkyl enoates as acceptor molecules in the presence of a chiral phase‐transfer catalyst has been demonstrated. The desired enantiomerically enriched β‐amino acid derivatives were obtained in up to 86% yield and with enantioselectivities of up to 37% ee. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:202–209, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21004     

CXCR4 Stimulates Macropinocytosis: Implications for Cellular Uptake of Arginine-Rich Cell-Penetrating Peptides and HIV

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Highlights? CXCR4 was identified as a receptor to stimulate cellular uptake of R12 peptide ? Interaction with R12 stimulates internalization of CXCR4 via macropinocytosis ? SDF-1α and HIV-1 gp120 protein also induce macropinocytosis ? Macropinocytic uptake of HIV-1 diminished the infection of host cells     

Projektive Skalen,Tschebyscheff-Polynome und Fibonacci-Zahlen

Summary. Let $\widehat{\widehat T}_n$ and $\overline U_n$ denote the modified Chebyshev polynomials defined by $\widehat{\widehat T}_n (x) = {T_{2n + 1} \left(\sqrt{x + 3 \over 4} \right) \over \sqrt{x + 3 \over 4}}, \quad \overline U_{n}(x) = U_{n} \left({x + 1 \over 2}\right) \qquad (n \in \mathbb{N}_{0},\ x \in \mathbb{R}).$ For all $n \in \mathbb{N}_{0}$ define $\widehat{\widehat T}_{-(n + 1)} = \widehat{\widehat T}_n$ and $\overline U_{-(n + 2)} = - \overline U_n$, furthermore $\overline U_{-1} = 0$. In this paper, summation formulae for sums of type $\sum\limits^{+\infty}_{k = -\infty} \mathbf a_{\mathbf k}(\nu; x)$ are given, where $\bigl(\mathbf a_{\mathbf k}(\nu; x)\bigr)^{-1} = (-1)^k \cdot \Bigl( x \cdot \widehat{\widehat T}_{\left[k + 1 \over 2\right] - 1} (\nu) +\widehat{\widehat T}_{\left[k + 1 \over 2\right]}(\nu)\Bigr) \cdot \Bigl(x \cdot \overline U_{\left[k \over 2\right] - 1} (\nu) + \overline U_{\left[k \over 2\right]} (\nu)\Bigr)$ with real constants $ x, \nu $. The above sums will turn out to be telescope sums. They appear in connection with projective geometry. The directed euclidean measures of the line segments of a projective scale form a sequence of type $(\mathbf a_{\mathbf k} (\nu;x))_{k \in \mathbb{Z}}$ where $ \nu $ is the cross-ratio of the scale, and x is the ratio of two consecutive line segments once chosen. In case of hyperbolic $(\nu \in \mathbb{R} \setminus] - 3,1[)$ and parabolic $\nu = -3$ scales, the formula $\sum\limits^{+\infty}_{k = -\infty} \mathbf a_{\mathbf k} (\nu; x) = {\frac{1}{x - q_{{+}\atop(-)}}} - {\frac{1}{x - q_{{-}\atop(+)}}} \eqno (1)$ holds for $\nu > 1$ (resp. $\nu \leq - 3$), unless the scale is geometric, that is unless $x = q_+$ or $x = q_-$. By $q_{\pm} = {-(\nu + 1) \pm \sqrt{(\nu - 1)(\nu + 3)} \over 2}$ we denote the quotient of the associated geometric sequence.

     

Orthocomplemented complete lattices and graphs

The problem I consider originates from Dörfler, who found a construction to assign an Orthocomplemented latticeH(G) to a graphG. By Dörfler it is known that for every finite Orthocomplemented latticeL there exists a graphG such thatH(G)=L. Unfortunately, we can find more than one graphG with this property, i.e., orthocomplemented lattices which belong to different graphs can be isomorphic. I show some conditions under which two graphs have the same orthocomplemented lattice.     

Atome im Doppeltopf-Potential gefangen. Interferenz zwischen zwei Bose-Einstein-Kondensaten

Die Nachricht von den ersten Realisierungen von Bose-Einstein-Kondensaten aus schwach wechselwirkenden Atomen im Sommer 1995 [1,2] (siehe auch Physik in unserer Zeit, 27, 200 (5/1996)) zog eine Welle neuer Forschungsaktivitäten nach sich. Wolfgang Ketterle vom Massachusetts Institute of Technology, MIT, und Kollegen gelang es kürzlich, zwei Bose-Einstein-Kondensate zur Interferenz zu bringen [3].     

Moenomycin a: New chemistry that allows to attach the antibiotic to reporter groups, solid supports, and proteins

Moenomycin A (18) on reaction with the diazonium salt derived from bifunctional (protected) 15 yields the coupling product 19 which on reduction is converted into the moenomycin thiol derivative 21. Thiol 21 has been used to prepare selectively moenomycin dansyl and biotin adducts 26 and 28, respectively. This work was performed with the aim to use moenomycin as a tool for studies of the transglycosylation step in peptidoglycan biosynthesis.     

A comparison of macro- and microscopic measurements of plutonium in contaminated soil from the Republic of the Marshall Islands

Plutonium contaminated soil from the Republic of the Marshall Islands has been studied to determine the spatial and volume characteristics of contamination on two scales: (1) in macroscopic masses, i.e., gram sized samples, and (2) in microscopic masses, i.e., 10's of grams to 1 mg. Three measures of volumetric homogeneity calculated from alpha track measurements on a plastic track detector (CR-39) are presented to quantitatively assess microspatial or microvolumetric variations. Data on the homogeneity of transuranic radioactivity is presented for four different particle size fractions of soil and in macro- and microvolumes. The nuclear track measurement technique is contrasted with radiochemistry/alpha spectrometry.