BASE-CATALYZED CONDENSATION OF BIS(DIETHYLPHOSPHONOMETHYL)-PHOSPHINIC AMIDES WITH ALDEHYDES1

Abstract

The reaction of the mono anion of bis(diethylphosphonomethyl)phosphinic amides (3) with aldehydes gives varying amounts of diethyl alkyl- or arylethenylphosphonates (10) and diethylphosphonomethylalkyl- or arylethenylphosphinic amides (7). When R in 3 is N,N-di-n-propylamino or N-cydohexyl-N-methylamino, the predominate product is 7 and this condensation is a satisfactory synthesis of vinylphosphinic amides which are potential antimetabolites of organic pyrophosphates.     

The Impact of Leaving Group Anomericity on the Structure of Glycosyl Cations of Protected Galactosides

It has been reported that fragments produced by glycosidic bond breakage in mass spectrometry-based experiments can retain a memory of their anomeric configuration, which has major implications for glycan sequencing. Herein, we use cryogenic vibrational spectroscopy and ion mobility-mass spectrometry to study the structure of B-type fragments of protected galactosides. Cationic fragments were generated from glycosyl donors carrying trichloroacetimidate or thioethyl leaving groups of different anomeric configuration. The obtained infrared signatures indicate that the investigated fragments exhibit an identical structure, which suggests that there is no anomeric memory in B-type ions of fully protected monosaccharides.     

Continuous‐Flow Oxidative Cyanation of Primary and Secondary Amines Using Singlet Oxygen

Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable‐temperature continuous‐flow LED‐photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α‐Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an in situ imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α‐aminonitriles. Primary α‐aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at –50 °C. This atom‐economic and protecting‐group‐free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert‐leucine hydrochloride from neopentylamine.     

New cytotoxic diterpenes from rondeletia panamensis (rubiaceae)

From the wood stem and stem bark of the Panamanian plant Rondeletia panamensis (Rubiaceae), three novel diterpenes have been isolated. The structure of oxidopanamensin (2) was determined by single crystal X-ray crystallography of the diacetate derivative. Panamensin (4) was correlated with oxidopanamensin (2) by epoxidation under alkali conditions and with rondeletin (6) by hydrogenation to 14,15-dihydrorondeletin (8). Of the three isolates, panamensin (4) and oxidopanamensin (2) were cytotoxic in the KB test system but rondeletin was inactive.     

Essay review: Symmetry not so Super

A group of researches has recently been linking the mutual dynamical interaction of a close pair of stars with the nuclear physics of the internal stellar structure. The rate at which the apse line of their orbit alters its orientation depends on the tidal and centrifugal distortion of such a closely associated pair; but for given dimensions of the two stars and their orbits this apse rotation is slower the more concentrated the material towards the centre of each star. This in turn depends on the evolutionary stage reached in depletion of their hydrogen as source of energy. The topic is here traced from the earliest papers by Russell in 1928 to the recent ones by Princeton astronomers in 1958. Critique of the potentialities of such work is finally suggested.     

Energy‐Efficient Solar Photochemistry with Luminescent Solar Concentrator Based Photomicroreactors

The sun is the most sustainable light source available on our planet, therefore the direct use of sunlight for photochemistry is extremely appealing. Demonstrated here, for the first time, is that a diverse set of photon‐driven transformations can be efficiently powered by solar irradiation with the use of solvent‐resistant and cheap luminescent solar concentrator based photomicroreactors. Blue, green, and red reactors can accommodate both homogeneous and multiphase reaction conditions, including photochemical oxidations, photocatalytic trifluoromethylation chemistry, and metallaphotoredox transformations, thus spanning applications over the entire visible‐light spectrum. To further illustrate the efficacy of these novel solar reactors, medicinally relevant molecules, such as ascaridole and an intermediate of artemisinin, were prepared as well.     

An ever-closer union? Examining the evolution of linkages of European equity markets via minimum spanning trees

The concept of a minimum spanning tree (MST) is used to study the process of comovements for 21 European Union stock market indices. We show how the minimum spanning tree and its related hierarchical tree evolve over time and describe the dynamics. Over the period studied, 1999-2006, the French equity market provides the main linkages in the system. The 2004 Accession states are more loosely connected to the other markets; they form two groupings, with the Czech Republic, Hungary, and Poland having tighter links to the main markets than the remaining Accession markets. Shorter distances between markets indicate a potential reduction of the benefits of international portfolio diversification in European markets, with the possible exception of those markets at the outer limits of the MST.