Abnormally low vicinal coupling constants for O-CH-CH in a highly strained five-membered-ring ether; The identity of loline and festucine

1969 ◽  
Vol 22 (9) ◽  
pp. 2021 ◽  
Author(s):  
AJ Aasen ◽  
CCJ Culvenor
Keyword(s):  
Membered Ring ◽  
Coupling Constants ◽  
Vicinal Coupling Constants ◽  
Highly Strained

Conformational Studies on 1,3-Dioxepanes. Part IV. Applications of Geminal Coupling Constants to Conformational Analysis of 1,3-Dioxepanes

1974 ◽  
Vol 52 (24) ◽  
pp. 4062-4071 ◽  
Author(s):  
T. Bruce Grindley ◽  
Walter A. Szarek
Keyword(s):  
Conformational Analysis ◽  
Coupling Constants ◽  
Conformational Studies ◽  
Vicinal Coupling Constants ◽  
Geminal Coupling ◽  
Derivatives Of ◽  
Acetal Carbon

The magnitude of —OCH2O— group geminal H,H coupling contants, the size of the vicinal coupling constants, and the tenets of conformational analysis were used to establish that in solution the conformation of the 1,3-dioxepane rings in derivatives of 1,3:2,5-di-O-methylenemannitol and 2,5-O-methylenemannitol is predominantly the twist-chair in which the C2 axis passes through the acetal carbon.

Chemie polyfunktioneller Moleküle, 108 Tetraedrische Kupfer(I)-Chelatkomplexe der Liganden Bis(diphenylphosphino)amin und Bis(diphenylphosphino)methan / Chemistry of Polyfunctional Molecules, 108 [1] Tetrahedral Copper(I) Chelate Complexes with the Ligands Bis(diphenylphosphino)amine and Bis(diphenylphosphino)methane

1991 ◽  
Vol 46 (12) ◽  
pp. 1699-1705 ◽  
Author(s):  
Jochen Ellermann ◽  
Falk A. Knoch ◽  
Klaus J. Meier
Keyword(s):  
Membered Ring ◽  
Monoclinic Space Group ◽  
Direct Reaction ◽  
Conductivity Data ◽  
Chelate Complexes ◽  
X Ray ◽  
Lattice Constants ◽  
H Nmr ◽  
Highly Strained ◽  
Nitrate Anions

Reaction of [Cu(PPh3)2(NO3)] (1) in acetone with bis(diphenylphosphino)amine (dppa, 2) yields [Cu(dppa)(PPh3)2]+NO3- (3a). [Cu(dppa)(PPh3)2]+PF6- (3b) has been synthesized by metatheses of 3a with NH4PF6. The salt [Cu(dppm)(PPh3)2]+PF6- (5b) has been prepared by an one batch reaction of [Cu(PPh3)2(NO3)] (1), bis(diphenylphosphino)methane (dppm, 4) and NH4PF6 in methanol, because [Cu(dppm)(PPh3)2]+NO3- (5a) could not be isolated by the direct reaction of 1 with 4. The IR, Raman, 31P{1H} NMR, 1H{31Ρ} NMR as well as the conductivity data are reported and discussed together with the X-ray crystal structure of 3a · 1.8 (CH3)2CO. The structure consists of copper atoms coordinated tetrahedrally by two PPh3 ligands and the chelating dppa ligand and features a highly strained four-membered ring. The distorted tetrahedral cations are hydrogen bridged to the nitrate anions. The colourless needles of 3a· 1.8 (CH3)2CO crystallize in the monoclinic space group C 2/c, with the lattice constants a = 4189.2(27); b = 1223.7(8); c = 2717.8(15) pm;β = 113.16(4)°.

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

P.M.R. spectra of heteroaromatic molecules containing bridgehead nitrogen atoms. V. Pyrrolo[a]quinoline

1976 ◽  
Vol 29 (4) ◽  
pp. 847 ◽  
Author(s):  
ML Heffernan ◽  
GM Irvine
Keyword(s):  
Ambient Temperature ◽  
Spin System ◽  
Variable Temperature ◽  
Membered Ring ◽  
Coupling Constants ◽  
Ring Proton ◽  
Temperature Study ◽  
Proton Resonances ◽  
Cdcl3 Solution ◽  
Bridgehead Nitrogen

The p.m.r. spectra of (CD3)2SO and CDCl3 solutions of pyrrolo[a]quinoline, a nine-spin system, have been analysed. In the former case, the various multiplets were sufficiently non-overlapping for detailed double-irradiation experiments to be performed in order to confirm the proton assignments and to determine the magnitudes and relative signs of several inter-ring coupling constants. For the CDCl3 solution, it was found that there was broadening of the five-membered ring proton resonances at ambient temperature. A variable-temperature study showed that the broadening was arising from the exchange of the H1 and H3 protons and that the effects of exchange could be avoided by running the spectra at or below -20�.

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