Synthesis of optically active hydroxyphosphonates

The reduction of dimenthyl ketophosphonates with sodium borohydride involves asymmetric induction at the α‐carbon atom, resulting in a small excess of the (R)‐enantiomer of the α‐hydroxyphosphonate formed. A higher ee purity was achieved if the reduction of chiral dimenthyl ketophosphonates was carried out by the chiral complex of NaBH₄‐L ‐proline, owing to the double asymmetric induction at the α‐carbon atom. The hydroxyphosphonates obtained were isolated in a diastereomerically pure state and were transformed to the optically active, free hydroxyalkylphosphonic acids. The (R)‐configuration of one of them was proved by X‐ray crystal structure analysis. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:133–139, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20391     

Dirhodium(II) Carboxylate Catalyzed Formation of 1,2,3‐Trisubstituted Indoles from Styryl Azides

Dirhodium(II)‐carboxylate complexes were discovered to promote the selective migration of acyl groups in trisubstituted styryl azides to form 1,2,3‐trisubstituted indoles. The styryl azides are readily available in three steps from cyclobutanone and 2‐iodoaniline.     

Optimised Desorption Electrospray Ionisation Mass Spectrometry Imaging (DESI-MSI) for the Analysis of Proteins/Peptides Directly from Tissue Sections on a Travelling Wave Ion Mobility Q-ToF

Desorption electrospray ionisation mass spectrometry imaging (DESI-MSI) is typically known for the ionisation of small molecules such as lipids and metabolites, in singly charged form. Here we present a method that allows the direct detection of proteins and peptides in multiply charged forms directly from tissue sections by DESI. Utilising a heated mass spectrometer inlet capillary, combined with ion mobility separation (IMS), the conditions with regard to solvent composition, nebulising gas flow, and solvent flow rate have been explored and optimised. Without the use of ion mobility separation prior to mass spectrometry analysis, only the most abundant charge series were observed. In addition to the dominant haemoglobin subunit(s) related trend line in the m/z vs drift time (DT) 2D plot, trend lines were found relating to background solvent peaks, residual lipids and, more importantly, small proteins/large peptides of lower abundance. These small proteins/peptides were observed with charge states from 1+ to 12+, the majority of which could only be resolved from the background when using IMS. By extracting charge series from the 2D m/z vs DT plot, a number of proteins could be tentatively assigned by accurate mass. Tissue images were acquired with a pixel size of 150 μm showing a marked improvement in protein image resolution compared to other liquid-based ambient imaging techniques such as liquid extraction surface analysis (LESA) and continuous-flow liquid microjunction surface sampling probe (LMJ-SSP) imaging.

Open image in new window

Graphical Abstract ?

     

Uncatalyzed,Regioselective Oxidation of Saturated Hydrocarbons in an Ambient Corona Discharge

Atmospheric pressure chemical ionization (APCI) in air or in nitrogen with just traces of oxygen is shown to yield regioselective oxidation, dehydrogenation, and fragmentation of alkanes. Ozone is produced from ambient oxygen in situ and is responsible for the observed ion chemistry, which includes partial oxidation to ketones and C?C cleavage to give aldehydes. The mechanism of oxidation is explored and relationships between ionic species produced from individual alkanes are established. Unusually, dehydrogenation occurs by water loss. Competitive incorporation into the hydrocarbon chain of nitrogen versus oxygen as a mode of ionization is also demonstrated.     

Examples of Non-Homeomorphic Harmonic Maps Between Negatively Curved Manifolds

Let M and N be closed non-positively curved manifolds, and letf:MN be a smooth map. Results of Eells and Sampson [1] showthat f is homotopic to a harmonic map , and Hartman [6] showedthat this is unique when N is negatively curved and f_*(₁ M)is not cyclic. Lawson and Yau conjectured that if f:MN is ahomotopy equivalence, where M and N are negatively curved, thenthe unique harmonic map homotopic to f would be a diffeomorphism.Counterexamples to this conjecture appeared in [2], and laterin [7] and [5]. There remains the question of whether a ‘topological’Lawson–Yau conjecture holds. 1991 Mathematics SubjectClassification 53C20, 55P10, 57C25, 58E20.     

Direct-to-video holographic readout in quantum wells for three-dimensional imaging through turbid media

Customized photorefractive quantum-well devices have been developed for real-time video acquisition of coherence-gated, three-dimensional images in turbid media. Large-field-of-view holographic imaging with direct video capture is now possible. We have evaluated the role of intensity-limited device performance in Fourier-plane and image-plane holography in such devices and, using near-infrared light, have imaged through turbid phantoms of 13 mean free paths' scattering depth with 50-microm transverse and 60-microm depth resolution.     

Asynchronous phase-modulated optical fiber-ring buffer

We investigate the dynamics of a 5-Gbit/s packet of ones and zeros loaded into a 0.5-kbit, phase-modulated optical fiber-ring buffer. A new mode of operation is explored in which the cavity length of the buffer is slightly detuned from the frequency driving the phase modulator. We examine the conditions for successful packet loading and the packet storage behavior. In addition, relaxation oscillations, which affected the storage time of previous high-speed optical ring buffers, are nearly eliminated with a cw holding beam, and significantly enhanced storage times are obtained.     

Zur Bestimmung des Titans

Analytical and Bioanalytical Chemistry -