The conformational properties of the gangliosides GM2 and GM1 based on 1H and,13C nuclear magnetic resonance studies

1984 ◽  
Vol 62 (6) ◽  
pp. 1034-1045 ◽  
Author(s):  
Subramaniam Sabesan ◽  
Klaus Bock ◽  
Raymond U. Lemieux
Keyword(s):  
Biological Properties ◽  
Carboxyl Group ◽  
Methyl Group ◽  
Acetylneuraminic Acid ◽  
Conformational Preferences ◽  
13C Nuclear Magnetic Resonance ◽  
Chemical Shift Data ◽  
Nuclear Overhauser ◽  
Shift Data ◽  
C Nmr

A comparison of the 1H and 13C nmr parameters for the disaccharide derivatives βDGal(1→ 4)βDGlcO(CH2)8COOCH3 (1), βDGalNAc(1 → 4)βDGalO(CH2)8COOCH3 (2), and βDGal(1 → 3)βDGalNAcO(CH2)2CH3 (3) allowed assignments of the signals observed for the asialo-GM2- and asialo-GM1-related synthetic haptens, βDGalNAc(1 → 4)βDGal(1→4)βDGlcO(CH2)8COOCH3 (4) and βDGal(1 → 3)βDGalNAc(1 → 4)βDGal(1 → 4)βDGlcO(CH2)8COOCH3 (5). 1H nuclear Overhauser enhancement studies confirmed the conformational preferences for 2 and 3 predicted by HSEA calculation. Comparison of the 1H and 13C spectra indicate that these preferences and that previously known for the lactoside (1) are closely maintained in the haptens 4 and 5. HSEA calculation indicates that the methyl group of methyl N-acetyl-α-D-neuraminic acid (10) prefers the orientation wherein the carboxyl group is near anti-periplanar to the methyl group. However, this orientation was not confirmed by saturation of the methyl group since no enhancement of either Ha-3 or He-3 was observed. On the other hand, saturation of Ha-3c of the αDNeuAc unit of the GM1-related pentasaccharide, βDGal(1 → 3)βDGalNAc(1 → 4)[αDNeuAc(2 → 3)]βDGal(1→4)α,βDGlc, caused strong enhancement of the signal for the aglyconic hydrogen, H-3bof the βDGal(1→4) unit. This observation, along with those of other nuclear Overhauser experiments, established that this pentasaccharide has the carboxyl group anti-periplanar to C-3b. Furthermore, the C-7c to C-9c chain of the αDNeuAc unit adopts nearly the same conformation for the compound in aqueous solution as exists for N-acetylneuraminic acid in the crystalline state. The HSEA calculation indicates important attractive interaction between this chain and the βDGalNAc unit of the aglycon. These conlcusions were extended to the GM2 and GM1 gangliosides by the comparison of chemical shift data. In these compounds, the carboxyl group projects over the hydrophobic α-side of the βDGalNAc unit and the polar OH-4c, NAc-5c, OH-7c groups project over the hydrophobic β-side of the lactose unit. Comments are made on the possible bearing of these topographical features on certain biological properties of gangliosides.

Aryldiazenido complexes: structure, fluxionality, and properties of the iridium ethylene aryldiazenido complex [(η5-C5Me5)Ir(C2H4)(p-N2C6H4OMe)][BF4] and a comparison with the analogous nitrosyl complex [(η5-C5Me5)Ir(C2H4)(NO)][BF4]

1995 ◽  
Vol 73 (7) ◽  
pp. 939-955 ◽  
Author(s):  
Xiaoqian Yan ◽  
Frederick W.B. Einstein ◽  
Derek Sutton
Keyword(s):  
Variable Temperature ◽  
Chloride Salt ◽  
Nitrosyl Complex ◽  
Reaction Conditions ◽  
Chemical Shift Data ◽  
Diazonium Ion ◽  
Centers Of Mass ◽  
Molecular Orbital Analysis ◽  
Shift Data ◽  
C Nmr

[Cp*Ir(C2H4)(N2Ar)][BF4] (1BF4; Ar = p-N2C6H4OMe) has been synthesized by reacting [ArN2] [BF4] with Cp*Ir(C2H4)2 at low temperature. An initial electrophilic attack of the incoming diazonium ion at iridium, followed by expulsion of C2H4, is postulated to account for the mild reaction conditions that are in sharp contrast to the usual inertness of the bis(ethylene) compound toward ligand substitution. The IR and nitrogen NMR data for 1BF4 and its 15Nα derivative unambiguously establish that the ArN2 ligand has the singly bent geometry in this complex in solution. The X-ray crystal structure confirms this for the solid state, and establishes that the plane of the aryldiazenido ligand is approximately perpendicular to the plane defined by the Ir atom and the centers of mass of the Cp* and ethylene ligands. An extended Hückel molecular orbital analysis of the singly bent aryldiazenido ligand has been carried out and satisfactorily accounts for the observed orientation of the ArN2 ligand. An analysis of the variable-temperature 1H and 13C NMR of 1BF4 indicates that both restricted rotation of the C2H4 ligand and a conformational isomerization of the aryldiazenido ligand are occurring, and ΔG≠270 for the ethylene rotation barrier is estimated at ≤ 51.5 ± 0.4 kJ mol−1. This is lower than the barrier of ΔG≠353 = 68.7 ± 0.2 kJ mol−1 determined previously for the analogous nitrosyl complex [Cp*Ir(C2H4)(NO)] [BF4] (2BF4) and it is suggested that in these half-sandwich complexes both NO and ArN2 function as single-faced π-acceptors, and in these circumstances ArN2 is the better π-acceptor. The ethylene in 1BF4 is readily displaced by PPh3 to give [Cp*Ir(PPh3)(N2Ar)][BF4] (3BF4). This reacts with NaBH4 to yield Cp*IrH(PPh3)(N2Ar) (4) in which the ArN2 ligand has switched to the doubly bent geometry, on the basis of the 15Nα NMR chemical shift data. Attempts to synthesize the corresponding chloro analogue 5 resulted in only the chloride salt of the singly bent ArN2 cation 3. For example, reaction of 3BF4 with HCl yields the aryldiazene complex [Cp*IrCl(PPh3)(NHNAr)] [BF4] (6), but deprotonation of this with Et3N yields 3Cl, not 5. Compound 1BF4 crystallized in the space group P21/n with a = 8.5780(10) Å, b = 20.5310(23) Å, c = 12.0310(15) Å, β = 93.500(10)°, and Z = 4. The structure was refined to Rf = 0.0281 on the basis of 2611 observed reflections with I°> 2.5σ(Io) in the range 2θ = 0–50° (Mo-Kα). Keywords: iridium, cyclopentadienyl, aryldiazenido, nitrosyl, ethylene.

scholarly journals N 6-Trimethyl-lysine metabolism. Structural identification of the metabolite 3-hydroxy-N6-trimethyl-lysine

1980 ◽  
Vol 188 (2) ◽  
pp. 521-527 ◽  
Author(s):  
Raymond F. Novak ◽  
Terrence J. Swift ◽  
Charles L. Hoppel
Keyword(s):  
Molecular Structure ◽  
Chemical Shift ◽  
Functional Group ◽  
Group Analysis ◽  
Resonance Spectroscopy ◽  
13C Nuclear Magnetic Resonance ◽  
Chemical Shift Data ◽  
Functional Group Analysis ◽  
13C Chemical Shift ◽  
Shift Data

1H and 13C nuclear-magnetic-resonance spectroscopy and functional-group analysis were used to determine the molecular structure of an isolated metabolite (IIb) of trimethyl-lysine as 3-hydroxy-N6-trimethyl-lysine, an important intermediate in the conversion of trimethyl-lysine into trimethylammoniobutyrate and carnitine [Hoppel, Cox & Novak (1980) Biochem. J.188, 509–519]. Functional-group analysis revealed the presence of a primary amine and reaction of metabolite (IIb) with periodate yielded 4-N-trimethylammoniobutyrate as a product, showing 2,3-substitution on the molecule and suggesting that the 3-substitution on the molecule may be an alcohol ([unk]CH–OH), amine ([unk]CH[unk]–NH2) or carbonyl ([unk]C=O) functional group. 1H integration ratios, 1H and 13C chemical-shift data and 1H and 13C signal multiplicities from the sample (IIb) were used to complete the identification of metabolite (IIb) as 3-hydroxy-N6-trimethyl-lysine. For example, the proton multiplet at δ 4.2p.p.m. and doublet at δ 4.1p.p.m., positions representative of amine or alcohol substitution on methylene carbon atoms, integration ratios of 1:1:2:9:4 and a positive ninhydrin test suggest 3-hydroxy-N6-trimethyl-lysine as the molecular structure for metabolite (IIb). 13C chemical-shift data obtained from the sample (IIb) and compared with several model compounds (trimethylammoniohexanoate, trimethyl-lysine and 3-hydroxylysine) resulted in generation of the spectrum of the metabolite and allowed independent identification of metabolite (IIb) as 3-hydroxy-N6-trimethyl-lysine. The 1H spectrum of erythro- and threo-3-hydroxylysine are presented for comparison, and the 1H and 13C n.m.r. spectra of the erythro-isomer support this analysis.

Effects of substitution on nitrogen on barriers to rotation of cyclic amides. Part I. Investigation of the rotational barier in 4-benzoyl-1-thia-4-azacyclohex-2-ene by 1H dynamic nuclear magnetic resonance spectroscopy

1977 ◽  
Vol 55 (6) ◽  
pp. 949-957 ◽  
Author(s):  
T. Bruce Grindley ◽  
B. Mario Pinto ◽  
Walter A. Szarek
Keyword(s):  
Variable Temperature ◽  
Activation Parameters ◽  
Resonance Spectroscopy ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Chemical Shift Data ◽  
Dynamic Nuclear Magnetic Resonance ◽  
Shift Data ◽  
C Nmr

The rotational barrier in 4-benzoyl-1-thia-4-azacyclohex-2-ene has been investigated by total line-shape analysis of variable temperature 1H nmr spectra in acetonitrile-d3. Separate treatment of the vinyl and methylene signals yielded sets of values for activation parameters which were in excellent agreement. Assignment of the major and minor rotational isomers was made from chemical-shift data derived from the 13C nmr spectrum at 243 K in acetonitrile-d3.

13C Nuclear Magnetic Resonance Spectra of Organic Sulfur Compounds: Cyclic Sulfides, Sulfoxides, Sulfones, and Thiones

1975 ◽  
Vol 53 (19) ◽  
pp. 2880-2890 ◽  
Author(s):  
M. S. Chauhan ◽  
I. W. J. Still
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Limited Data ◽  
Organic Sulfur Compounds ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Chemical Shift Data ◽  
Derivatives Of ◽  
Shift Data ◽  
Methyl Phenyl

13C Chemical shift data have been obtained for more than 50 thiochromanone and related sulfoxide and sulfone derivatives. The assignments of the various resonances in the most important of these have been made using the limited data already available and also by comparison with certain model compounds, such as thioanisole, diphenyl sulfide, and the corresponding sulfoxides and sulfones.Within each of these three series and in a fourth which comprises derivatives of thiochromone, including three α, β-unsaturated thiones, we have examined the effects on 13C chemical shift of substitution at various positions in the thiochromanone skeleton. Among the substituents examined in this context are methyl, phenyl, methoxyl, bromine, and carbomethoxyl. Attempts to compare the 13C chemical shifts for the thiochromanone series with those in a few oxygen containing analogs and in a small number of structurally similar analogs are also discussed.

Revised structure for the γ-lactone derived from acid treatment of dihydroisopimaric acid

1976 ◽  
Vol 54 (3) ◽  
pp. 418-422 ◽  
Author(s):  
John W. ApSimon ◽  
Andrew M. Holmes ◽  
Helmut Beierbeck ◽  
John K. Saunders
Keyword(s):  
Acid Treatment ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Ring Fusion ◽  
Spin Lattice ◽  
Structure Revision ◽  
Chemical Shift Data ◽  
Shift Data ◽  
C Nmr

The γ-lactone obtained from acid treatment of dihydroisopimaric acid was found to have a cis-A/B ring fusion. This structure revision was based on 13C nmr chemical shift data and spin–lattice relaxation time (T1) measurements. Using the same methods, the δ-lactone derived from the same acid was shown to have the previously proposed structure.

scholarly journals Revisit to 25R/25S Stereochemical Analysis of Spirostane-type Steroidal Sapogenins and Steroidal Saponins via 1H NMR Chemical Shift Data

2012 ◽  
Vol 7 (6) ◽  
pp. 1934578X1200700
Author(s):  
Pawan K. Agrawal ◽  
Torsten Burkholz ◽  
Claus Jacob
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Steroidal Saponins ◽  
Methyl Group ◽  
H Nmr ◽  
Stereochemical Analysis ◽  
Chemical Shift Data ◽  
The Difference ◽  
Shift Data ◽  
1H Nmr Chemical Shift

An approach based on the difference (Δab = δa – δb) between 1H NMR chemical shifts (δa, δb) of the geminal protons of oxymethylene (H2-26) (Δab = <0.2 for 25 R; Δab = >0.5 for 25 S) is proposed for ascertaining 25 R/25 S orientation of the 27-methyl group for (22 R)-spirostane-type steroidal sapogenins and steroidal saponins. These studies suggested the 25 R-orientation of the 27-Me group for the steroidal saponins isolated by Temraz et al. from Tribulus alatus.

13C NMR spectroscopy of heterocycles: 1-phenyl-3-aryl/t-butyl-5-arylpyrazoles

2017 ◽  
Vol 23 (2) ◽  
pp. 125-131 ◽  
Author(s):  
Amy N. Hockstedler ◽  
Beatrice A. Edjah ◽  
Saajid Z. Azhar ◽  
Hadrian Mendoza ◽  
Nicole A. Brown ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Phenyl Group ◽  
13C Nmr Spectroscopy ◽  
Aryl Group ◽  
Torsion Angles ◽  
Chemical Shift Data ◽  
Molecular Modeling Studies ◽  
Shift Data ◽  
C Nmr

AbstractA series of chalcones 1–12 were converted to pyrazolines (1Pi–12Pi) by reaction with phenylhydrazine followed by DDQ oxidation to produce the corresponding pyrazoles (1Pz–12Pz). Three 1-phenyl-3-t-butyl-5-arylpyrazoles (13Pz–15Pz) were synthesized using an analogous approach. Molecular modeling studies predicted the 5-aryl group of the pyrazoles for both series to have a torsion angle of 52°–54° whereas the 1-phenyl group was predicted to have 35°–37° torsion angles. The 3-aryl group was predicted to be essentially coplanar (−3°) with the pyrazole system in the first series. 13C NMR data for both series, 1Pz–12Pz and 13Pz–15Pz, were collected in DMSO-d6 at 50°C. A plot of the C4 chemical shifts for 1Pz–12Pz versus Hammet constants for 5-aryl substituents yielded a very good linear correlation (R2=0.96) with a slope of 1.5. The chemical shift data for C4 showed little or no dependence on 3-aryl substituents. The result for 13Pz–15Pz, despite only three points, was consistent with the first series results and yielded a ρ value of 2.0. Distal transmission of substituent effects (5-aryl groups) to C4 of the pyrazole system was reduced by roughly 50–60% of that of the analogous planar isoxazole system, but are not consistent with results for the similarly twisted 4-bromoisoxazoles.

Synthesis and characteristics of ethylenediamine-N,N'-di-S-α-isovalerate and isomers of its cobalt(III) complexes

1982 ◽  
Vol 47 (1) ◽  
pp. 210-216 ◽  
Author(s):  
Milan Strašák ◽  
František Bachratý ◽  
Jaroslav Majer
Keyword(s):  
Amino Acids ◽  
Absolute Configuration ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Chemical Parameters ◽  
Methyl Group ◽  
Nmr Data ◽  
Physico Chemical ◽  
Natural Amino Acids ◽  
C Nmr

The synthesis and physico-chemical parameters are described of a new complexone based on natural amino acids, viz. ethylenediamine-N,N'-di-S-α-isovalerate (SS-EDDIV). 1H- and 13C-NMR data revealed that the methyl group in the substance are not equivalent. The isomers of the cobalt(III) complex with the asymmetric tetradentate SS-EDDIV ligand were prepared and separated; their characteristics are given. The absolute configuration of two of the five theoretically feasible isomers was determined based on their electronic absorption spectra and circular dichroism data.

Sign in / Sign up

Export Citation Format

Share Document