Control of disaccharide conformation by π-stacking

2003 ◽  
Vol 81 (5) ◽  
pp. 364-375 ◽  
Author(s):  
Jonathan Watts ◽  
Jesús Jiménez-Barbero ◽  
Ana Poveda ◽  
T Bruce Grindley
Keyword(s):  
Nmr Spectroscopy ◽  
Molecular Modelling ◽  
Phenyl Ring ◽  
Glycosidic Linkage ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Π Stacking ◽  
Nuclear Overhauser ◽  
Derivatives Of

The conformations of a series of derivatives of the disaccharide α-L-fucopyranosyl-(1[Formula: see text]3)-2-acetamido-2-deoxy-D-glucopyranoside, part of the Lex determinant, were studied by molecular modelling using the MM3* forcefield and by 1H NMR spectroscopy. Unusually shielded O-benzyl protons were observed in the 1H NMR spectrum of phenyl 2,3,4-tri-O-benzyl-α-L-fucopyranosyl-(1[Formula: see text]3)-2-deoxy-2-phthalimido-1-thio-α-D-glucopyranoside and assigned to the 2-O-benzyl group. This observation was explained by a shift in the population of the conformational mixture present about the glycosidic linkage from the positive Ψ region in the unsubstituted disaccharide to the negative Ψ region induced by π-stacking between the phthalimide and the 2-O-benzyl phenyl ring. The experimental nuclear Overhauser enhancements confirm the accuracy of the calculations.Key words: disaccharide, conformation, π-stacking, Lex determinant, NOE measurements, MM3 calculations.

The synthesis and conformational properties of the diastereoisomeric βDGal(1→4)βDGlcNAc(1→6)6-C-CH3-D-Gal trisaccharides

1982 ◽  
Vol 60 (1) ◽  
pp. 81-86 ◽  
Author(s):  
Raymond U. Lemieux ◽  
Ting C. Wong ◽  
Henning Thøgersen
Keyword(s):  
Monoclonal Antibody ◽  
Nmr Spectroscopy ◽  
Molecular Modelling ◽  
Computer Assisted ◽  
Glycosidic Linkage ◽  
H Nmr ◽  
Conformational Preferences ◽  
Conformational Properties ◽  
Derivatives Of

The trisaccharide βDGal(1 → 4)βDGlcNAc(1 → 6)DGal was known to be bound strongly by the so-called anti-I Ma monoclonal antibody. In order to help assess the conformation about the 1 → 6 glycosidic linkage that is accepted by the antibody combining site, the conformationally well-defined βDGal(1 → 4)βDGlcNAc(1 → 6) derivatives of 7-deoxy-L-glycero-D-galacto-heptopyranose and 7-deoxy-D-glycero-D-galacto-heptopyranose were synthesized. The conformational preferences for these trisaccharides were established by 1H nmr spectroscopy and rationalized by computer-assisted molecular modelling.

Arene–manganese and arene–rhenium compounds of formula (arene)M(CO)2(SiCl3)

1997 ◽  
Vol 75 (5) ◽  
pp. 531-535 ◽  
Author(s):  
Valerie M. Hansen ◽  
Jonathan L. Male ◽  
Roland K. Pomeroy
Keyword(s):  
Nmr Spectroscopy ◽  
Metal Atom ◽  
Good Yield ◽  
Free Rotation ◽  
Nmr Spectrum ◽  
Manganese Compound ◽  
Restricted Rotation ◽  
H Nmr ◽  
Arene Ligand ◽  
Derivatives Of

Derivatives of formula (arene)M(CO)2(SiCl3) (M = Mn, Re) have been prepared in moderate to good yield by the reaction of M(CO)5(SiCl3) and the appropriate arene (with heptane in those cases where the arene was a solid) in an evacuated sealed tube at 230–260 °C for 12–24 h, depending on the arene and the metal. Carefully purified reagents were necessary to obtain satisfactory yields. The (η6-1,4-C6H4tBu2)M(CO)2(SiCl3) complexes in solution exhibit free rotation of the arene ring about the metal atom to −120 °C as ascertained by 1H NMR spectroscopy. The manganese compound did show the onset of decoalescence of two of the signals due to the arene ligand in the 13C{1H} NMR spectrum in CD2Cl2, solution below −90 °C. This, however, is interpreted in terms of restricted rotation of the tert-butyl substituent rather than restricted rotation of the arene ring. Keywords: arene, manganese, rhenium, restricted rotation.

Monitoring the encapsulation of chlorin e6 derivatives into polymer carriers by NMR spectroscopy

2019 ◽  
Vol 23 (11n12) ◽  
pp. 1576-1586 ◽  
Author(s):  
Sara Pfister ◽  
Luca Sauser ◽  
Ilche Gjuroski ◽  
Julien Furrer ◽  
Martina Vermathen
Keyword(s):  
Relaxation Time ◽  
Nmr Spectroscopy ◽  
Core Region ◽  
Chlorin E6 ◽  
Polypropylene Glycol ◽  
Polymer Carriers ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Dynamic Methods ◽  
Derivatives Of

The encapsulation of five derivatives of chlorin e6 with different hydrophobicity and aggregation properties into a series of five poloxamer-type triblock copolymer micelles (BCMs) with varying numbers of polyethylene and polypropylene glycol (PEG, PPG) units was monitored using 1H NMR spectroscopy. NMR chemical shift and line shape analysis, as well as dynamic methods including diffusion ordered spectroscopy (DOSY) and T1 and T2 relaxation time measurements of the chlorin and the polymer resonances, proved useful to assess the chlorin–BCM compatibility. The poloxamers had high capability to break up aggregates formed by chlorins up to intermediate hydrophobicity. Physically entrapped chlorins were always localized in the BCM core region. The loading capacity correlated with chlorin polarity for all poloxamers among which those with the lowest number of PPG units were most efficient. DOSY data revealed that relatively weakly aggregating chlorins partition between the aqueous bulk and micellar environment whereas more hydrophobic chlorins are well retained in the BCM core region, rendering these systems more stable. T1 and T2 relaxation time measurements indicated that motional freedom in the BCM core region contributes to encapsulation efficiency. The BCM corona dynamics were rather insensitive towards chlorin entrapment except for the poloxamers with short PEG chains. The presented data demonstrate that 1H NMR spectroscopy is a powerful complementary tool for probing the compatibility of porphyrinic compounds with polymeric carriers such as poloxamer BCMs, which is a prerequisite in the development of stable and highly efficient drug delivery systems suitable for medical applications like photodynamic therapy of tumors.

Heteroassociation of meso-sulfonatophenylporphyrins with β- and γ-cyclodextrin

2001 ◽  
Vol 05 (05) ◽  
pp. 465-473 ◽  
Author(s):  
ZOUBIR EL-HACHEMI ◽  
JOAN-ANTON FARRERA ◽  
HECTOR GARCÍA-ORTEGA ◽  
OSCAR RAMÍREZ-GUTÍERREZ ◽  
JOSEP M. RIBÓ
Keyword(s):  
Inclusion Complexes ◽  
Bulk Water ◽  
Hydrophobic Region ◽  
Water Solutions ◽  
H Nmr ◽  
Cyclodextrin Inclusion Complexes ◽  
Cyclodextrin Inclusion ◽  
Cyclodextrin Cavity ◽  
Nuclear Overhauser ◽  
Derivatives Of

The effect of the addition of β- and γ-cyclodextrin (β-CD, γ-CD) to water solutions ( D 2 O ) of the 4'-sulfonato derivatives of meso-tetraphenylporphyrin (TPPS4, TPPS3, TPPS2o and TPPS2a) was studied by 1 H NMR at several temperatures. In all cases the disaggregation of the porphyrin homoassociates was detected, although in most cases it was only partial. Nuclear Overhauser signals (ROESY) show that cyclodextrin inclusion complexes were formed with TPPS4, TPPS3, and TPPS2o, but not with TPPS2a. These complexes include the sulfonatophenyl groups as guest, but not the hydrophobic phenyl substituents. The geometry of the complexes corresponds to that in which the sulfonatophenyl substituent is introduced through the secondary face of β-CD and through the primary face of γ-CD. In the inclusion complexes the polar sulfonato group is inside the cyclodextrin cavity but near to the hydrophilic interface with the bulk water. This explains the absence of complexation in the case of cationic porphyrins such as 5,10,15,20-tetrakis(N-methylpyridin-4-yl)porphyrin (TMPyP), and the decrease in the solubility when the β-CD complex of 5,15-bis(4-sulfonatophenyl)porphyrin (DPPS2o) forms. Complexes of the cyclodextrins with porphyrin homoassociates were also detected. This indicates that the heteroassociation avoids the formation of staggered stacks of porphyrin homoassociates, but has less effect on the association through the hydrophobic region of the phenyl substituents. This last type of aggregation, which is not significantly affected by the addition of α-CD, explains why the hydrophobic phenyl substituents are not complexed by the cyclodextrins.

An evaluation of high resolution nuclear magnetic resonance experiments and protocols in the structure elucidation of organic molecules. I. A relatively simple system, brucine

1985 ◽  
Vol 63 (2) ◽  
pp. 483-490 ◽  
Author(s):  
Michael A. Bernstein ◽  
Laurance D. Hall
Keyword(s):  
High Resolution ◽  
Chemical Shift ◽  
Structural Information ◽  
Nuclear Overhauser Effect ◽  
Proton Spectrum ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
Nmr Methods

Using a combination of one-dimensional (1D) and two-dimensional (2D) high resolution nmr methods, the 1H nmr spectrum of brucine was fully assigned. The 2D J-resolved and homonuclear chemical shift correlated (COSY) experiments provided assignments without full structural information; this was obtained from nuclear Overhauser effect (nOe) enhancement experiments (1D and 2D). With the proton spectrum fully assigned, proton-bearing carbons in the 13C nmr spectrum were easily assigned using the 2D heteronuclear chemical shift correlation map (CSCM) experiment.

Imidazole Nucleosides, V. Synthesis of 3′-Fluoro-3′-deoxy-ribofuranosides of 4(5)-Amino-imidazoIe-5(4)carboxamide

1999 ◽  
Vol 54 (8) ◽  
pp. 1055-1060 ◽  
Author(s):  
Hans Guglielmi ◽  
Markus Dachtler ◽  
Klaus Albert
Keyword(s):  
Nmr Spectroscopy ◽  
Elemental Analysis ◽  
H Nmr ◽  
Anti Cancer ◽  
Derivatives Of ◽  
Fluoro Derivatives

The synthesis of the 3′-fluoro-derivatives of 5-amino-1-(β-D-ribofuranosyl)imidazole-4- carboxamide (AICA-riboside) and the isomeric 4-amino-1(β-D-ribofuranosyl)imidazole-5- carboxamide (iso-AICA-riboside) are described. Structures were confirmed by elemental analysis, UV and 1H NMR spectroscopy. The anti-viral and anti-cancer activities of these imidazole nucleosides were tested.

Structural studies on the polysaccharide portion of "A-band" lipopolysaccharide from a mutant (AK1401) of Pseudomonas aeruginosa strain PAO1

1991 ◽  
Vol 69 (8) ◽  
pp. 1273-1280 ◽  
Author(s):  
Todd L. Arsenault ◽  
Donald W. Hughes ◽  
David B. MacLean ◽  
Walter A. Szarek ◽  
Andrew M. B. Kropinski ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Structural Studies ◽  
Coherence Transfer ◽  
Strain Pao1 ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Main Structural Feature ◽  
Nuclear Magnetic Resonance Spectra ◽  
Structure Formula ◽  
Nuclear Overhauser

AK1401 is a mutant of Pseudomonas aeruginosa strain PAO1 (serotype 05) that does not express O-antigen, but does express "A-band" lipopolysaccharide (LPS). The polysaccharide portion of the A-band LPS (A-PS) from AK1401 was found to consist mainly of D-rhamnose, with smaller amounts of 3-O-methylrhamnose, ribose, mannose, glucose, and a 3-O-methylhexose. 1H nuclear magnetic resonance spectra of the intact A-PS indicated that the main structural feature was a repeating trisaccharide of α-D-rhamnose having the following structure:[Formula: see text]The 1H NMR spectrum of the repeating unit was completely assigned through the use of 2D shift-correlated and relayed coherence transfer NMR spectroscopy. The linkage positions and sequence of residues were found by nuclear Overhauser enhancement difference spectroscopy. Key words: Pseudomonas aeruginosa, lipopolysaccharide, 1H NMR.

Synthesis of cyclopentane analogs of (2′- and 3′-deoxy-erythro-pentofuranosyl and ribofuranosyl)-2-thiouracil nucleosides

1986 ◽  
Vol 64 (8) ◽  
pp. 1620-1629 ◽  
Author(s):  
Lucjan J.J. Hronowski ◽  
Walter A. Szarek
Keyword(s):  
Sulfur Atom ◽  
Nmr Spectra ◽  
Aqueous Ammonia ◽  
Synthetic Route ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Synthetic Intermediates ◽  
Derivatives Of ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

Three new carbocyclic analogs of nucleosides having the 2-thiouracil base have been synthesized. The cyclopentyl groups in these nucleosides are (±)-{(1β,3α,4β)-3-hydroxy-4-(hydroxyrnethyl)cyclopentyl} (see 31), (±)-{(1β,2α,4β)-2-hydroxy-4-(hydroxymethyl)cyclopentyl} (see 32), and (±)-{(1β,2α,3α,4β)-2,3-dihydroxy-4-(hydroxymethyl)cyclopentyl} (see 33). The nucleosides were prepared by coupling the appropriate hydroxy derivatives of cis-3-aminocyclopentanemethanol with 3-ethoxypropenoyl isothiocyanate (21) followed by cyclization in 15 N aqueous ammonia to give the 2-thiouracil nucleosides. In addition a modified and shortened synthetic route is described for the synthesis of (±)-(1β,2α,3α,4β)-4-amino-2,3-dihydroxy-cyclopentanemethanol (19). The 1H nmr spectra at 200 MHz of all of the synthetic intermediates, the 2-thiouracil nucleosides, and of the corresponding carbocyclic analogs of uracil nucleosides are discussed. It is shown that each nucleoside has a characteristically unique 1H nmr spectrum and that in general the protons in the sulfur-containing compounds resonate at lower fields than those in the corresponding oxygen-containing compounds. The magnitude of this downfield shift is inversely related to the number of bonds separating a particular proton from the sulfur atom.

scholarly journals Design, Synthesis, and Characterization of Novel Thiol-Derivatized Ibuprofen Monolayer Protected Gold Clusters

2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Kuan-Han Lee ◽  
Yu-Sheng Lin ◽  
Po-Jui Huang
Keyword(s):  
Nmr Spectroscopy ◽  
Gold Clusters ◽  
Hydroxyl Group ◽  
Synthesis And Characterization ◽  
Nmr Spectrum ◽  
Design Synthesis ◽  
H Nmr

A series of new thiol-derivatized ibuprofen monolayer protected gold clusters have been prepared by amidation of ibuprofen with alkyl alcohol or aminophenol affording the carboxamides, N-hydroxyalkyl amide2, and N-hydroxyphenyl amide6, which were then tosylated withp-toluenesulfonyl chloride at hydroxyl group to give3and7. Reactions of3and7with NaSH afforded the mercapto derivatives4and8. Conducting Brust’s reaction with a 3 : 1 mole ratio of thiolate ibuprofen/AuCl4-yielded polydisperse thiol-derivatized ibuprofen-MPCs5and9. All compounds have been identified by NMR, MS, UV, and IR spectroscopies. Compounds4and8and the MPCs5and9have been investigated by using the method of1H NMR spectroscopy. The broadening of the signals from 0.8 to 2.0 ppm in1H NMR spectrum of MPCs5and9confirmed the success of the conjugation of thiol-containing derivatives with nanogold cluster.

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