The conformations of prostacyclin and related prostaglandins

1985 ◽  
Vol 63 (5) ◽  
pp. 1143-1149 ◽  
Author(s):  
Helmut Beierbeck ◽  
George Kotovych ◽  
Makiko Sugiura
Keyword(s):  
Nmr Spectroscopy ◽  
High Field ◽  
Coupling Constants ◽  
Side Chain ◽  
Spectroscopic Parameters ◽  
H Nmr ◽  
Vicinal Coupling Constants ◽  
Nuclear Overhauser ◽  
Chain Conformations ◽  
Ring Conformations

The conformations of prostacyclin, PGI2, and three of its analogues, 6R- and 6S-PGI1 and carbacyclin, were studied by high field 1H nmr spectroscopy. The cis-bicyclo- and cis-oxabicyclo[3.3.0]octane ring conformations were completely assigned. The minima for the pseudorotational conformations are observed at 7E/12E for PGI2, [Formula: see text] for 6R-PGI1, and 6E/11E for 6S-PGI1, and carbacyclin. The data indicate that each molecule adopts a narrow pseudolibrational range, if not a single conformation. The α- and ω-side chain conformations were characterized, but not unambiguously. Vicinal coupling constants and nuclear Overhauser enhancements proved to be the most useful spectroscopic parameters in this study.

scholarly journals NMR solution conformation of heparin-derived tetrasaccharide

1996 ◽  
Vol 318 (1) ◽  
pp. 93-102 ◽  
Author(s):  
Dmitri MIKHAILOV ◽  
Kevin H. MAYO ◽  
Ioncho R. VLAHOV ◽  
Toshihiko TOIDA ◽  
Azra PERVIN ◽  
...  
Keyword(s):  
Chair Conformation ◽  
Coupling Constants ◽  
Solution Conformation ◽  
1H And 13C Nmr ◽  
Small Deviations ◽  
J Coupling Constants ◽  
Nuclear Overhauser ◽  
Nuclear Overhauser Effects ◽  
Dynamics Simulations ◽  
Ring Conformations

The solution conformation of the homogeneous, heparin-derived tetrasaccharide ΔUA2S(1 → 4)-α-d-GlcNpS6S(1 → 4)-α-l-IdoAp2S(1 → 4)-α-d-GlcNpS6S (residues A, B, C and D respectively, where IdoA is iduronic acid) has been investigated by using 1H- and 13C-NMR. Ring conformations have been defined by J-coupling constants and inter-proton nuclear Overhauser effects (NOEs), and the orientation of one ring with respect to the other has been defined by inter-ring NOEs. NOE-based conformational modelling has been done by using the iterative relaxation matrix approach (IRMA), restrained molecular dynamics simulations and energy minimization to refine structures and to distinguish between minor structural differences and equilibria between various ring forms. Both glucosamine residues B and D are in the 4C1 chair conformation. The 6-O-sulphate group is oriented in the gauche–trans configuration in the D ring, whereas in the B ring the gauche–gauche rotomer predominates. Uronate (A) and iduronate (C) residues are mostly represented by 1H2 and 2S0 twisted boat forms, respectively, with small deviations in expected coupling constants and NOEs suggesting minor contributions from other A and C ring conformations.

E-Homolupane Derivatives Substituted in Position 17 and 22a. 1H NMR, 13C NMR and IR Spectra

1995 ◽  
Vol 60 (4) ◽  
pp. 619-635 ◽  
Author(s):  
Václav Křeček ◽  
Stanislav Hilgard ◽  
Miloš Buděšínský ◽  
Alois Vystrčil
Keyword(s):  
Nmr Spectra ◽  
2D Nmr ◽  
Coupling Constants ◽  
Side Chain ◽  
Oxidation Reactions ◽  
H Nmr ◽  
Complete Assignment ◽  
Nmr Techniques ◽  
Intramolecular Association ◽  
C Nmr

A series of derivatives with various oxygen functionalities in positions 17,22a or 19,20 was prepared from diene I and olefin XVI by addition and oxidation reactions. The structure of the obtained compounds was confirmed by 1H NMR, 13C NMR and IR spectroscopy. The kind of intramolecular association of the 17α-hydroxy group was studied in connection with modification of the side chain and substitution in position 22a. Complete assignment of the hydrogen signals and most of the coupling constants was accomplished using a combination of 1D and 2D NMR techniques. The 1H and 13C NMR spectra are discussed.

scholarly journals IDENTIFICATION AND SEQUENCING BY NMR SPECTROSCOPY OF THE CARBOHYDRATE MOIETY IN A SAPONIN FROM Barringtonia asiatica

2010 ◽  
Vol 1 (3) ◽  
pp. 120-124
Author(s):  
Rymond J Rumampuk
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Coupling Constants ◽  
Carbohydrate Moiety ◽  
Glycosidic Linkage ◽  
1H And 13C Nmr ◽  
Heteronuclear Correlation ◽  
Vicinal Coupling Constants ◽  
Nmr Signals

A trisaccharide chain in a saponin from the seeds of Barringtonia asiatica has been identified and sequenced as {[b-D-galactopyranosyl(1®3)- b-D-glucopyranosyl(1®2)]-b-D-glucuronopyranosyloxy} using a combination of homonuclear and heteronuclear correlation NMR spectroscopy. The 1H and 13C NMR signals of the sugar residues can be determined and distinguished from one other by use of the HMQC-TOCSY technique. Anomeric configurations were unambiguously assigned from the vicinal coupling constants 3JH-1,H-2 of the anomeric protons. Inter-glycosidic linkage assignments were elucidated using  HMBC.   Keyword: Barringtonia asiatica, carbohydrate, saponin, NMR

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.

sHigh resolution 1H nuclear magnetic resonance studies of a flavine and its product with MoCl4

1977 ◽  
Vol 55 (4) ◽  
pp. 575-582 ◽  
Author(s):  
T. Roberie ◽  
N. S. Bhacca ◽  
J. Selbin
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Binding Sites ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Side Chain ◽  
Magnetic Resonance Studies ◽  
H Nmr ◽  
Metal Atoms ◽  
1H Nuclear Magnetic Resonance

The high resolution 1H nmr spectra of the substituted flavine, 3-N-methyltetraacetylriboflavine (3-Me-TARF), and its non-aqueous solution complexes with Gd(fod)3, Eu(fod)3, MoCl4, and MoCl4•2CH3(CH2)2CN, were studied in order to try to discern the binding sites of the flavine as it attaches to the molybdenum. Evidence was found that all three metal atoms, Gd(III), Eu(III), and Mo(IV), are attached in solution not only by the primary binding (chelating) sites of the flavine, viz., the O-4 and N-5 atoms, but also by an acetyl oxygen atom, at the C-4′ site of the ribityl side chain. 300 MHz spectra of the 3-Me-TARF have permitted the coupling constants for the side chain methine and methylene protons to be obtained.

Studies related to antitumor antibiotics. Part XXIV. High field 1H nmr analysis and conformations of saframycins A and C

1981 ◽  
Vol 59 (20) ◽  
pp. 2945-2952 ◽  
Author(s):  
J. William Lown ◽  
Alummoottil V. Joshua ◽  
Hsiao-Hsiung Chen
Keyword(s):  
High Field ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Coupling Constants ◽  
Cytotoxic Action ◽  
Antitumor Antibiotics ◽  
Dna Templates ◽  
H Nmr ◽  
Proton Chemical Shifts ◽  
Unambiguous Assignment

A detailed analysis of the high field (400 MHz) 1H nmr spectra of the basic antitumor antibiotics saframycin A and C in CDCl3, C6D6, and in aqueous DMSO solutions has been carried out. Selective double irradiation experiments permitted the unambiguous assignment of all the proton chemical shifts and coupling constants. Consideration of the magnitudes of the latter together with specific nOe experiments permits assignment of molecular geometry and average conformations in solution. Selective shifts occurring in DMSO–D2O solutions upon addition of CF3COOD identified the 12-N atom as the site of protonation which result bears directly on the acid promoted binding of these antibiotics to DNA templates as part of their cytotoxic action.

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