Diastereoselective Coordination of Chiral Phosphine Substituted Thioamide Ligands

Abstract

Homochiral thioamides are forming diastereomeric molybdenum and tungsten complexes in different ways (type 1–3) and different stereoselectivities (1 and 2: > 99%de, 3:0%de). The dissolved complexes 1 epimerized slowly at room-temperature.     

A rigorous foundation of an easy-to-apply approximation method for bound state problems

Recently the application of a non-expensive scattering theory method to bound state problems has been proposed on the grounds of intuitive arguments. Subsequent realistic calculations have manifested advantageous features of the method especially in problems in which the asymptotic behaviour of the wave function is important. Here it is rigorously proven that the method is convergent, and mathematically correct procedures are described that speed up convergence and make the approximate energies approach the exact value from one side only. The general considerations are visualized by numerical results of a model problem.     

Enhanced peptide beta-sheet affinity by metal to ligand coordination

A histidine-coordinating metal complex substituted with methoxypyrrole amino acids (MOPAS) as a peptide beta-sheet binder shows high affinity for a H(2)N-His-Leu-Leu-Val-Phe-OMe pentapeptide in DMSO solution. Within the complex, a beta-sheet conformation is induced into the pentapeptide by weak intra-assembly interactions with the MOPAS units.     

A luminescent receptor with affinity for N-terminal histidine in peptides in aqueous solution

Crown ethers of suitable size are the perfect artificial host compounds for ammonium ion binding, but the rather low affinity in aqueous solution prevents their use at physiological conditions. We report here the synthesis and properties of a luminescent benzo crown ether with a pendant copper imidodiacetic acid complex, which coordinates with high affinity to histidine. The emission intensity of the benzo crown ether increases significantly in the presence of ammonium ions in methanol. At physiological conditions in buffered water at pH 7.5 these interactions are too weak to be detected. If an ammonium ion and an imidazole moiety are present in the analyte, such as in His-Lys-OMe or His-OMe, high binding affinity in aqueous solution is restored. The binding event is signaled by an increase in emission intensity, which can even be observed with the naked eye. This allows the selective detection of small peptides containing N-terminal histidine or histidine among all other amino acids at physiological conditions.     

Die affine duale Ebene und eine ihr aufgeprägte Maßbestimmung in einer Abbildung auf denR 4

Ohne ZusammenfassungPh. Furtwängler zum 70. Geburtstag.Ausführliche Wiedergabe des am 13. IX. 1938 anläßlich des Deutschen Physiker- und Mathematikertages in Baden-Baden unter dem Titel Darstellende Geometrie der dualen Ebene gehaltenen Vortrages.     

Heteronucleare clustersysteme : XVIII. Methylidyn-, silylidyn- und germylidyn-nanocarbonyl-triiridium-cluster

NaIr(CO)₄ reacts with Cl₃CL (L = CH₃, C₆H₅), Cl₃SiCH₃ or Cl₃GeCH₃ to form the novel cluster compounds (CO)₉Ir₃CCH₃ (I), (CO)₉Ir₃CC₆H₅ (II), (CO)₉IrSi- CH₃ (III) and (CO)₉Ir₃GeCH₃ (IV), respectively. Comparison of the IR spectra in the ν(CO) region with those of the structurally well established methylidyne clusters (CO)₉Co₃CL shows equivalent symmetry conditions. The analytical and IR data enable possible structures to be proposed.     

Concise Syntheses of Marine (Bis)indole Alkaloids Meridianin C,D, F,and G and Scalaridine A via One-Pot Masuda Borylation-Suzuki Coupling Sequence

N-Protected 3-iodoindoles were reacted with (di)azine halides in a sequentially Pd-catalyzed one-pot fashion, i.e., by Masuda borylation–Suzuki coupling (MBSC) sequence. This methodology was successfully applied to the concise syntheses of marine indole alkaloids meridianin C, D, F, and G, as well as to the bisindole alkaloid scalaridine A, which were obtained in moderate to excellent yield.