A fluorescent water-soluble naphthalimide-based receptor for saccharides with highest sensitivity in the physiological pH range

A new water-soluble fluororeactand for the optical detection of saccharides is presented. We have combined the functional naphthalimide fluorophore with the well-known ability of boronic acids to bind to the diol moiety of saccharides. The fluororeactand exhibits sensitivity in the mM range, absorbance and emission in the visible spectral range, large Stokes' shift and fluorescence increase in the physiological pH range.     

The word problem for involutive residuated lattices and related structures

It will be shown that the word problem is undecidable for involutive residuated lattices, for finite involutive residuated lattices and certain related structures like residuated lattices. The proof relies on the fact that the monoid reduct of a group can be embedded as a monoid into a distributive involutive residuated lattice. Thus, results about groups by P. S. Novikov and W. W. Boone and about finite groups by A. M. Slobodskoi can be used. Furthermore, for any non-trivial lattice variety , the word problem is undecidable for those involutive residuated lattices and finite involutive residuated lattices whose lattice reducts belong to . In particular, the word problem is undecidable for modular and distributive involutive residuated lattices. The author would like to thank the Deutsche Telekom Stiftung for financial support. Received: 10 November 2005     

Use of copper(II)/diamine catalysts in the desymmetrisation of meso-diols and asymmetric Henry reactions: comparison of (−)-sparteine and (+)-sparteine surrogates

Four new copper(II)/diamine complexes comprising some (+)-sparteine surrogates and a cyclohexane-derived diamine were prepared and evaluated as chiral catalysts in desymmetrisation of meso-diols and asymmetric Henry reactions. Mono-benzoylation reactions generated two products with high enantioselectivity (90:10 to 97:3 er). Asymmetric Henry reactions gave nitro alcohols in 90:10 to 98:2 er. Notably, the sense of induction with the (+)-sparteine surrogates was opposite to that obtained using the copper(II)/(−)-sparteine complex. One of the nitro alcohol products was utilised in a concise synthesis of a chiral morpholine.     

Application of iridium pincer complexes in hydrogen isotope exchange reactions

Iridium pincer complex catalyzed hydrogen to deuterium exchange could be achieved using aromatic and heteroaromatic substrates. The reactions proceed under mild conditions and with high regioselectivity. The efficiency of the hydrogen isotope exchange reaction depends on the electronic properties of the pincer complex catalyst.     

Chemistry of a geminal frustrated Lewis pair featuring electron withdrawing C6F5 substituents at both phosphorus and boron

Hydroboration of the electron poor phosphine (1-propenyl)P(C(6)F(5))(2) with Piers' borane [HB(C(6)F(5))(2)] gave the geminal frustrated Lewis pair (C(6)F(5))(2)P-CH(Et)-B(C(6)F(5))(2). It undergoes 1,2-addition reactions to an alkene and an alkyne and to the C=N bond of an isocyanate. With mesityl azide it undergoes a 1,3-addition reaction.     

Dynamics of interatomic Coulombic decay in quantum dots

In this work we demonstrate that the interatomic Coulombic decay (ICD), an ultrafast electron relaxation process known for atoms and molecules, is possible in general binding potentials. We used the multiconfiguration time-dependent Hartree method for fermions to study ICD in real time in a two-electron model system of two potential wells. Two decay channels were identified and analyzed by using the box stabilization analysis as well as by evaluating the autocorrelation function and measuring the outgoing electron flux during time-propagations. The total and partial ICD widths of an excited state localized in one potential well as a function of the distance between the two potentials was obtained. Finally, we discuss the results with a view to a possible application of ICD in quantum dot technology.     

A simple method for analyzing 51V solid-state NMR spectra of complex systems

Five vanadium complexes as models for biological systems were investigated using ⁵¹V-MAS–NMR spectroscopy. All spectra show an uncommon line shape, which can be attributed to a shorter relaxation time of the satellite transition in contrast to the central one. A method for the reliable analysis of such kind of spectra is presented for the first time and the most important NMR parameters of the investigated complexes (quadrupolar coupling constant C_Q, asymmetry of the EFG tensor η_Q, isotropic chemical shift δ_iso, chemical shift anisotropy δ_σ and asymmetry of the CSA tensor η_σ) are presented. These results are of particular importance with respect to the analysis of the ⁵¹V-MAS–NMR spectra of vanadium moieties in biological matrices such as vanadium chloroperoxidase, which show hitherto unexplained low intensity of the satellite sideband pattern.     

Application of accelerator mass spectrometry to macromolecules: preclinical pharmacokinetic studies on a polybisphosphonate

Data on the use of accelerator mass spectrometry (AMS) in conjunction with in vivo studies of macromolecular drugs are scarce. The present study shows the versatility of this technique when investigating the pharmacokinetics (PK) of a macromolecular drug candidate, a polybisphosphonate conjugate (ODX). The aforementioned is a polymer (molecular weight ~30 kDa) constituting a carbohydrate backbone with covalently linked ligands (aldendronate and aminoguanidine) and is intended for treatment of osteoporosis and the therapy of bone metastasis from prostate cancer. The conjugate is prepared through partial oxidation of the carbohydrate and sequential coupling of the ligands by reductive amination. ¹⁴ C was incorporated in the conjugate by means of coupling a commercially available ¹⁴ C‐lysine in the conjugation sequence. Fifteen rats were injected intravenously with ¹⁴ C‐labelled ODX (150 µg, 14 Bq/rat) and blood samples were collected at 1, 2, 4, 6, and 24 h post‐injection (3 rats/time point). Liver, spleen and kidney samples were collected at 4 and 24 h post‐injection. Blood from each time point (triplicate) were collected for AMS measurement determining the isotopic ratio (¹⁴ C/¹² C) and consequently the drug concentration in blood. ODX showed a transient presence in blood circulation; 93% of the total dose was cleared from the circulation within 1 h. The half‐life after 1 h was estimated to be about 3 h; 0.7% of the administered ¹⁴ C dose of ODX remained in circulation after 24 h. The major ¹⁴ C accumulation was in the liver, the spleen and the kidneys indicating the probable route of metabolism and excretion. This study demonstrates the versatility of AMS for pharmacological in vivo studies of macromolecules. Labelling with ¹⁴ C is relatively simple, inexpensive and the method requires minimal radioactivity, eliminating the need for radioprotection precautions in contrast to methods using scintillation counting. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation of strained axially chiral (1,5)naphthalenophanes by photo-dehydro-Diels-Alder reaction

The preparation of 10 (1,5)naphthalenophanes (10a-j) by photo-dehydro-Diels-Alder (PDDA) reaction is described. Owing to hindered rotation around the biaryl axis, compounds 10 are axially chiral and the separation of enantiomers by chiral HPLC was demonstrated in three cases (10a,b,e). The absolute configuration of the isolated enantiomers could be unambiguously determined by comparison of calculated and measured circular dichroism (CD) spectra. Furthermore, we analyzed ring strain phenomena of (1,5)naphthalenophanes 10. Depending on the length of the linker units, one can distinguish three classes of naphthalenophanes. Compounds 10a-c are highly strained (E(STR) = 7-31 kcal/mol), and the strain is caused by small bond angles in the linker unit and deformation of the naphthalene moiety. Another type of strain is observed if the linker unit becomes relatively long (10g,h) originating from transannular interactions and is comparable with the well-known strain of medium sized rings. The naphthalenophanes 10d-f with a linker length of 10-14 atoms are only marginally strained. To clearly discriminate the different sources of strain, we defined two geometrical parameters (average central dihedral angle δ(C) and naphthalene thickness D(N)) and demonstrated that they are well-suited to indicate naphthalene deformation of our naphthalenophanes 10 as well as of ten model naphthalenophanes (I-X) with different linker lengths and linking positions.