Schmidt reaction on camphor. Part I. Structure of the products

1987 ◽  
Vol 65 (1) ◽  
pp. 137-149 ◽  
Author(s):  
Norman R. Hunter ◽  
M. Zafar Khan ◽  
Kirk Marat ◽  
Ossama A. L. El-Kabbani ◽  
Louis T. J. Delbaere
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Field ◽  
Major Product ◽  
Schmidt Reaction ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Amide Linkage ◽  
Amino Amide

A reinvestigation of the major product from the Schmidt reaction on camphor has led to the assignment of the structure as 1,9,9-trimethyl-3-oxo-2,8-diazabicyclo[3.3.1]nonane (5). The structure has been established by high-field proton and carbon-13 nuclear magnetic resonance, as well as degradation to the imine ester 4. Confirmation of the structure of 5 was achieved by X-ray crystallography. Compound 5, C10H18N2O, crystallized in space group P21/a with a = 14.934(1) Å, b = 10.973(1) Å, c = 12.341(1) Å, β = 92.0°, and Z = 8. The relatively rare cis amide linkage is present in the molecule. In addition to the amino amide 5, the Schmidt reaction on camphor leads to small amounts of the tetrazole 8 and the imine nitrile 9.

The crystal structure of ethyl-Z-3-amino-2-benzoyl-2-butenoate and measurement of the barrier to E,Z-isomerization

1980 ◽  
Vol 58 (17) ◽  
pp. 1821-1828 ◽  
Author(s):  
Gary D. Fallon ◽  
Bryan M. Gatehouse ◽  
Allan Pring ◽  
Ian D. Rae ◽  
Josephine A. Weigold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Energy Of Activation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Free Energy Of Activation ◽  
Nuclear Magnetic

Ethyl-3-amino-2-benzoyl-2-butenoate crystallizes from pentane as either the E (mp 82–84 °C) or the Z-isomer (mp 95.5–96.5 °C). The E isomer is less stable, and changes spontaneously into the Z, which bas been identified by X-ray crystallography. The structure is characterised by an N–H/ester CO hydrogen bond and a very long C2—C3 bond (1.39 Å). Nuclear magnetic resonance methods have been used to measure the rate of [Formula: see text] isomerization at several temperatures, leading to the estimate that the free energy of activation at 268 K is 56 ± 8 kJ.

Structure and nuclear magnetic resonance spectra of 6-bromo-3,3′,4′,5,7-penta-O-methylcatechin

1985 ◽  
Vol 63 (8) ◽  
pp. 2176-2180 ◽  
Author(s):  
F. W. B. Einstein ◽  
E. Kiehlmann ◽  
E. K. Wolowidnyk
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Title Compound ◽  
Bromine Atom ◽  
Heterocyclic Ring ◽  
Equatorial Orientation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic Resonance Spectra ◽  
Ring Conformations

The title compound has been synthesized by selective debromination of 6,8-dibromocatechin and indirect methylation of the resulting 6-bromocatechin via its pentaacetate. The structure of C20H23BrO6 has been determined by X-ray crystallography. The compound crystallizes in the space group P1 with a = 9.589(3) Å, b = 11.576(3) Å, c = 11.326(3) Å, α = 118.80(3)°, β = 93.23(3)°, γ = 111.44(3)°, ρc = 1.481 g cm−3, and Z = 2. Intensities were measured for 2584 independent reflections (2θ < 45°) of which 2213 were observed (I > 3.0σ(I)) and used in subsequent refinement (final R values were R = 0.0268 and Rw = 0.0344). Crystallographic and pmr data confirm the position of the bromine atom at C-6, the trans-diaxial arrangement of H-2/H-3 and the quasi-equatorial orientation of the 3,4-dimethoxyphenyl group (ring B). The two heterocyclic ring conformations are consistent with the expected flexibility of the molecule.

Synthesis and conformation studies by x-ray crystallography and nuclear magnetic resonance of cyclo(L-Phe-L-Pro-D-Ala)2

1984 ◽  
Vol 106 (13) ◽  
pp. 3844-3850 ◽  
Author(s):  
Gopinath Kartha ◽  
K. Krishna Bhandary ◽  
Kenneth D. Kopple ◽  
Anita Go ◽  
Peng Peng Zhu
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic

scholarly journals Supersize Cp! Tetrabenzo[a,c,g,i]fluorenyl complexes of yttrium

2017 ◽  
Vol 95 (4) ◽  
pp. 363-370 ◽  
Author(s):  
Jianlong Sun ◽  
David J. Berg ◽  
Brendan Twamley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ethylene Polymerization ◽  
Nmr Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
Trinuclear Cluster ◽  
Polymerization Catalyst ◽  
Dynamic Nuclear Magnetic Resonance ◽  
Trimethylsilyl Isocyanate

The synthesis of tetrabenzo[a,c,g,i]fluorenyl (Tbf) yttrium dialkyl complexes, (Tbf)Y(CH2SiMe3)2(L) (L = tetrahydrofuran (THF), 1; L = bipy, 2), by direct protonolysis of the tris(alkyl) complex, Y(CH2SiMe3)3(THF)2, are reported. The X-ray crystal structures of 1 and 2 display the helical twisting typically observed for the Tbf ligand. Dynamic nuclear magnetic resonance (NMR) studies on 1 show a barrier to Tbf helical inversion (epimerization or “wagging”) of 38.1 ± 0.5 kJ mol−1. The reaction of 1 with acidic hydrocarbons such as 1,3-bis(trimethylsilyl)cyclopentadiene or trimethylsilylacetylene results in protonolysis to form the mixed Cp derivative [(Tbf){C5H3(SiMe3)2}Y(CH2SiMe3)(THF)] (3) or [(Tbf)Y(CCSiMe3)2(THF)]n (4), respectively. In the case of 4, a small amount of the trinuclear cluster (Tbf)Y3(μ3-CCSiMe3)2(μ2-CCSiMe3)3(CCSiMe3)3(THF)2 (5) was isolated and characterized by X-ray crystallography. Dialkyl 1 undergoes smooth insertion of trimethylsilyl isocyanate to afford [(Tbf)Y{κ2-(N,O)-Me3SiN(Me3SiCH2)CO}2(THF)] (6) but it does not react with alkenes. Treating 1 with [Ph3C]+[B(C6F5)4]− in bromobenzene generates a moderately active ethylene polymerization catalyst (36 kg mol−1 h−1 bar−1).

scholarly journals Unravelling Conformational Aspects of Milk Protein Structure—Contributions from Nuclear Magnetic Resonance Studies

Foods ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1128
Author(s):  
Tatijana Markoska ◽  
Todor Vasiljevic ◽  
Thom Huppertz
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Calcium Phosphate ◽  
Dairy Products ◽  
Tertiary Structure ◽  
Whey Proteins ◽  
Milk Proteins ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic

Changes in the molecular structure and association of milk proteins lead to many desirable (under controlled conditions) or undesirable characteristics of dairy products. Several methods have been used to study the structure of milk proteins and changes therein in different environments. Whey proteins are an excellent model for secondary structure studies using circular dichroism (CD), Fourier-transform infrared spectroscopy (FTIR) and tertiary structure studies using X-ray crystallography and nuclear magnetic resonance (NMR). However, caseins, the most abundant protein class in milk, are far more difficult to characterize. The tertiary structure of caseins cannot be observed by X-ray crystallography due to the inability to crystallize caseins. However, NMR is an appropriate approach for structural elucidation. Thus far, NMR was applied on specific peptides of individual caseins of the molecules including phosphoserine centers and colloidal calcium phosphate. The literature focuses on these parts of the molecule due to its importance in building the sub-unit particles involving individual caseins and calcium phosphate nanoclusters. This review focuses on present structural studies of milk proteins using NMR and their importance in dairy processing.

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