Search results for "nuclear magnetic resonance"
showing 10 items of 1743 documents
- conformational preference of , -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid
1985
Abstract The 1 H and 13 C nmr spectra of exo , exo -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d 6 or alkaline D 2 O, clearly show that it exists in a boat - chair -conformation with equatorial carboxyl groups, thus being the first case of boat - chair preference of a bicyclo[3.3.1] nonan-9-one due to the presence of exo , exo -2,4- substituents.
Synthesis of peptides with α,β‐dehydroamino acids, III. Debenzyloxycarbonylation and detrifluoroacetylation of dehydroalanine and dehydrophenylalanin…
1985
The removal of amino protecting groups from a series of twelve model Z-3) or TFA-dipeptides of dehydroalanine and (Z)-dehydrophenylalanine was investigated. During this deprotection, peptides with Δ Ala are prone to side reactions to a higher extent than those with Δ Phe. Therefore it is interesting to note that from the Δ Ala peptides, the Z group can be split off in preparative manner with HCO2NH4 in the presence of Pd C (Table 4). Synthese von Peptiden mit α,β-Dehydroaminosauren, III.– Debenzyloxycarbonylierung und Detrifluoracetylierung von Dehydroalanin- und Dehydrophenylalanin-Peptiden An einer Serie von zwolf Z-3) oder TFA-Modellpeptiden mit Dehydroalanin und (Z)-Dehydrophenylalanin …
<strong>Synthesis and Platinum (II) Complexes of Different Polyazacyclophane Receptors</strong>
2015
During the last years, research on coordination chemistry of platinum has aroused great interest due to their potential biological applications. Herein, we report the interaction of PtCI42- with different polyazacyclophanes containing a pyridine unit as aromatic spacer. Formation of complexes has been studied by 1H and 195Pt NMR spectroscopy. Analysis of the recorded spectra of D2O solutions containing L and PtCl42- in a 1:1 molar ratio at acidic pH shows the evolution with time of the 1H and 195Pt signals. Different crystal structures have been solved by X-ray diffraction analysis. At acidic pHs, the metal ion is coordinated by the central amino group of the macrocyclic cavity and three ch…
Conformation of dehydropentapeptides containing four achiral amino acid residues - controlling the role of L-valine.
2014
Structural studies of pentapeptides containing an achiral block, built from two dehydroamino acid residues (ΔZPhe and ΔAla) and two glycines, as well as one chiral L-Val residue were performed using NMR spectroscopy. The key role of the L-Val residue in the generation of the secondary structure of peptides is discussed. The obtained results suggest that the strongest influence on the conformation of peptides arises from a valine residue inserted at the C-terminal position. The most ordered conformation was found for peptide Boc-Gly-ΔAla-Gly-ΔZPhe-Val-OMe (3), which adopts a right-handed helical conformation.
Deuteron Magnetic Resonance Study of Order and Dynamics in Liquid Crystal Polymers
1984
Abstract Thermotropic nematic polyesters, specifically deuterated at different positions of the polymer chain are studied by multiple pulse dynamic NMR. Analysis of the NMR experiments is achieved, employing a comprehensive model, based on the stochastic Liouville equation. Computer simulations provide the orientational distributions and conformations of the polymer chains and the correlation times of the various motions. In the anisotropic melt the correlation times for chain reorientation and trans-gauche-isomerization are in the range of 0.1–10 ns. Decreasing the temperature of the solid polymer first freezes the intermolecular motions. Thus, below the glass transition only intramolecula…
Synthesis and thermoresponsive properties of four arm, amphiphilic poly(tert-butyl-glycidylether)-block-polyglycidol stars
2011
Abstract A series of four arm stars with copolymer arms composed of poly(tert-butyl-glycidylether)-b-polyglycidol were prepared using a multi-step process based on anionic ring-opening polymerization. Control of the length of the arms and the number of functional (hydroxyl) reactive groups was achieved by anionic polymerization. Stars with molar masses up to 12200 g/mol were prepared. The amphiphilic character of the star structure was varied using different polyglycidol block lengths. The star structure and molar mass of the obtained stars were characterized by SEC–MALLS and NMR spectroscopy. The temperature behavior of an aqueous solution of the obtained polymers was also investigated. Th…
Structure elucidation of new oleanane-type glycosides from three species of Acanthophyllum
2010
From the roots of three species of Acanthophyllum (Caryophyllaceae), two new gypsogenic acid glycosides, 1 and 2, were isolated, 1 from A. sordidum and A. lilacinum, 2 from A. elatius and A. lilacinum, together with three known saponins, glandulosides B and C, and SAPO50. The structures of 1 and 2 were established mainly by 2D NMR techniques as 23-O-β-D-galactopyranosylgypsogenic acid-28-O-β-D-glucopyranosyl-(13)-[β-D-glucopyranosyl-(16)]-β-D-galactopyranoside (1) and gypsogenic acid-28-O-β-D-glucopyranosyl-(13)-[β-D-glucopyranosyl-(16)]-β-D-galactopyranoside (2). The cytotoxicity of several of these saponins was evaluated against two human colon cancer cell lines (HT-29 and HCT 116). Copyr…
Iodonium complexes of the tertiary amines quinuclidine and 1-ethylpiperidine
2021
Iodonium complexes incorporating tertiary amines have been synthesised to study and explore why such species comprised of alkyl amines are relatively rare. The complexes were characterised in solution (1H and 15N NMR spectroscopy) and the solid state (SCXRD), and analysed computationally. peerReviewed
The Influence of the Amide Linkage in the FeIII-Binding Properties of Catechol-Modified Rosamine Derivatives
2015
The two new fluorescent ligands RosCat1 and RosCat2 contain catechol receptors connected to rosamine platforms through an amide linkage and were synthesized by using microwave-assisted coupling reactions of carboxyl- or amine-substituted rosamines with the corresponding catechol units and subsequent deprotection. RosCat1 possesses a reverse amide, whereas RosCat2 has the usual oriented amide bond (HNCO vs. CONH, respectively). The ligands were characterized by means of NMR spectroscopy, mass-spectrometry, and DFT calculations and X-ray crystallography studies for RosCat1. The influence of the amide linkage on the photophysical properties of the fluorescent ligands was assessed in different …
Muskelrelaxantien, 4. Mitt. Monoacylbutyroguanamine
1986
Die Umsetzung von Butyroguanamin (1) mit den Carbonsaureanhydriden 2a−f bei 80–120° fuhrt zu den Monoacylbutyroguanaminen 3a−f, deren Struktur durch IR-, 1H-NMR- und MS-Spektren untermauert wird. Unter den hier beschriebenen Verbindungen weisen insbesondere 3e muskelrelaxierende und antidiabetische und 3a trichomonazide und antivirale Wirksamkeit auf, wahrend mit 3b−d herbizide Wirkungen beobachtet werden. Muscle Relaxants, IV: Monoacylbutyroguanamines Reaction of butyroguanamine (1) with the carboxylic acid anhydrides 2a−f at 80–120°C leads to the monoacylbutyroguanamines 3a−f, the structure of which is supported by IR, 1H-NMR, and mass spectra. Among the compounds described here, particul…