Stereoselective epimerization of pilocarpine in aqueous solution as determined by 13C nuclear magnetic resonance spectroscopy

1976 ◽  
Vol 54 (13) ◽  
pp. 2094-2100 ◽  
Author(s):  
George A. Neville ◽  
Fariza B. Hasan ◽  
Ian C. P. Smith
Keyword(s):  
Degradation Products ◽  
Parent Compound ◽  
Imidazole Ring ◽  
Alkaline Treatment ◽  
Resonance Spectroscopy ◽  
Open Chain ◽  
Similar Treatment ◽  
13C Nuclear Magnetic Resonance ◽  
Hydrolysis Of ◽  
C Nmr

Cleavage and recyclization of the lactone ring of pilocarpine (1) and of isopilocarpine (2) in D2O with varying pD have been studied by 13C nmr spectroscopy. Alkaline treatment (pD 10–13) results in rapid epimerization of pilocarpine to form isopilocarpine (28 ± 3% at 30 °C) and hydrolysis of the parent compound(s) to form the open chain pilocarpinate (isopilocarpinate). By contrast, isopilocarpine does not epimerize to pilocarpine under similar treatment. A mechanism is discussed for the epimerization of pilocarpine and the nonepimerization of the isopilocarpine is rationalized. pKa values of 5.7 and 8.5, respectively, have been determined for pilocarpinic acid and for the dissociation of the protonated quaternary nitrogen of the imidazole ring of pilocarpine. A basis for assay of degradation products in aqueous pilocarpine solutions utilizing differences in 13C chemical shift for C-8 is discussed.

Hydrolysis of Sesquimustards

2003 ◽  
Vol 56 (4) ◽  
pp. 309 ◽  
Author(s):  
Timothy D. St Quintin ◽  
D. Ralph Leslie ◽  
J. Grant Collins
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Contaminated Soil ◽  
Resonance Spectroscopy ◽  
Sulfonium Ions ◽  
13C Nuclear Magnetic Resonance ◽  
Hydrolysis Of

The hydrolysis of the sesquimustards 1,2-bis(2-chloroethylthio)ethane (QN2) and 1,3-bis(2-chloroethylthio) propane (QN3) has been studied by 1H and 13C nuclear magnetic resonance spectroscopy. For both sesquimustards, stable cyclic sulfonium ions were observed in hydrolysis experiments in a 1 : 1 mixture of [D6]acetone and D2O. The cyclic sulfonium ions, which persist in the aqueous solution for up to a week, are likely to retain some toxicity and could possibly be used as markers for sesquimustards in the analysis of mustard-contaminated soil for chemical weapons treaty verification. The formation of a macrocyclic oxadithiaether was also demonstrated for QN2 but not QN3.

scholarly journals Chemical constituents of the physodes of brown algae. Characterization by 1H and 13C nuclear magnetic resonance spectroscopy of oligomers of phloroglucinol from Fucus vesiculosus (L.)

1977 ◽  
Vol 55 (9) ◽  
pp. 1575-1582 ◽  
Author(s):  
James S. Craigie ◽  
A. Gavin McInnes ◽  
Mark A. Ragan ◽  
John A. Walter
Keyword(s):  
Molecular Weight ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Chemical Constituents ◽  
Fucus Vesiculosus ◽  
Resonance Spectroscopy ◽  
Low Molecular Weight ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

Alcoholic extracts of Fucus vesiculosus contain small quantities of low molecular weight polyphenols derived from phloroglucinol and 2,2′,4,4′,6,6′-hexahydroxybiphenyl. 1H and 13C nmr were used to identify two of these as 4-(2′′,4′′,6′′-trihydroxyphenoxy)-2,2′,4′,6,6′-pentahydroxybiphenyl and 4-(2′′-(2′′′,4′′′,6′′′-trihydroxyphenoxy)-4′′,6′′-dihydroxyphenoxy)-2,2′,4′, 6,6′-pentanydroxybiphenyl.

Direct non-invasive observation of metabolism in living cells by 13C nuclear magnetic resonance spectroscopy

1980 ◽  
Vol 58 (17) ◽  
pp. 1839-1846 ◽  
Author(s):  
Gerardo Burton ◽  
Robert L. Baxter ◽  
J. Martyn Gunn ◽  
Philip J. Sidebottom ◽  
Paul E. Fagerness ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Anaerobic Metabolism ◽  
Aminolevulinic Acid ◽  
Living Cells ◽  
Resonance Spectroscopy ◽  
Whole Cells ◽  
Non Invasive ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

Applications of 13C nmr in following the metabolism and fate of 13C enriched substrates in whole cells are described. Studies on the elaboration of coproporphyrinogens I (2a) and III (2b) from [5-13C]-δ-aminolevulinic acid (1) and [11-13C-porphobilinogen (PBG, 3), in Rhodopseudomonasspheroides and Propionibacteriumshermanii, respectively, the randomization of 13C from [3-13C]-propionate by P. shermanii, the biosynthesis of citrate, gentisalcohol (4), and patulin (5) from [2-13C]-acetate by Penicilliumurticae, and the anaerobic metabolism of [1-13C]-glucose in rabbit erythrocytes are reported.

On the chemistry and high field nuclear magnetic resonance spectroscopy of rapamycin

1980 ◽  
Vol 58 (6) ◽  
pp. 579-590 ◽  
Author(s):  
John A. Findlay ◽  
Lajos Radics
Keyword(s):  
High Field ◽  
Nmr Spectra ◽  
Resonance Spectroscopy ◽  
X Ray ◽  
Conformational Isomers ◽  
H Nmr ◽  
Neutral Compounds ◽  
Complete Assignment ◽  
Hydrolysis Of ◽  
C Nmr

Base catalysed hydrolysis of rapamycin (C51H79NO13) affords six neutral compounds identified by chemical and spectroscopic means as 2a, 3b, 3d, 5, 2,4-dimethylphenol, and L(−)-piperidine-2-carboxylic acid 6, and whose generation has been plausibly rationalized. These findings as well as detailed analyses of 13C nmr and 1H nmr spectra provide independent corroboration of the X-ray derived rapamycin crystal structure 1. Structurally homogeneous in the solid state, rapamycin is found to occur in solutions as a mixture of two conformational isomers (approximately 4:1). Through nearly complete assignment of the high field 1H (400 MHz) and 13C (100.6 MHz) nmr spectra, the isomerism is shown to be associated with trans–cis rotation of an amidic bond within the 31-membered macrolide ring. The predominant form corresponds to the conformer portrayed by X-ray analysis.

On the structure, chemistry, and 13C nuclear magnetic resonance of ravidomycin

1983 ◽  
Vol 61 (2) ◽  
pp. 323-327 ◽  
Author(s):  
John A. Findlay ◽  
Jia-Sen Liu ◽  
Lajos Radics
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Cross Correlation ◽  
Degradation Products ◽  
Chemical Degradation ◽  
Antitumor Antibiotic ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Nuclear Magnetic

Full spectral details in support of the earlier proposed structure 1a for the antitumor antibiotic ravidomycin are presented together with an account of chemical degradation products. A complete corroboration of structure is provided by cross correlation of 1H and 13C nmr for ravidomycin and its diacetate 1b.

Substituent effects of phosphorus-containing groups on aromatic reactivity. Determination of substituent constants by 13C nuclear magnetic resonance spectroscopy

1977 ◽  
Vol 55 (21) ◽  
pp. 3681-3685 ◽  
Author(s):  
Tomasz A. Modro
Keyword(s):  
Substituent Effects ◽  
Resonance Spectroscopy ◽  
Benzene Derivatives ◽  
13C Nuclear Magnetic Resonance ◽  
Phosphorus Containing ◽  
Substituent Constants ◽  
Parameter Approach ◽  
Reactivity Determination ◽  
C Nmr

13C nmr spectra have been obtained for a series of benzene derivatives substituted with phosphorus-containing groups of the type PZ2, P(O)Z2, and P(S)Z2. Inductive and resonance substituent constants were determined from the shielding of meta and para carbon atoms according to the dual-substituent parameter approach. Possible mechanisms of substituent effects of PIII and PV derived functional groups are discussed and in some cases compared with effects of the analogous nitrogen derivatives.

Analysis of the hydrolysates from cured and uncured urea-formaldehyde (UF) resins with two F/U mole ratios

Holzforschung ◽  
2018 ◽  
Vol 72 (9) ◽  
pp. 759-768 ◽  
Author(s):  
Muhammad Adly Rahandi Lubis ◽  
Byung-Dae Park
Keyword(s):  
Functional Groups ◽  
Degradation Products ◽  
Urea Formaldehyde ◽  
Chemical Species ◽  
Gel Permeation Chromatography ◽  
Hydrolysis Time ◽  
Water Hydrolysis ◽  
Hydrolysis Of ◽  
C Nmr

Abstract Uncured and cured urea-formaldehyde (UFcured) resins prepared with formaldehyde/urea (F/U) mole ratios of 1.0 and 1.2 and at the catalyst levels of 1, 2 and 3% NH4Cl were hydrolyzed for 5, 15 and 30 min and the degradation products were evaluated using gel permeation chromatography, Fourier-transform infrared (FTIR) and liquid carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopies. The molar masses of the degradation products, their functional groups and structures were determined. An extended hydrolysis time and higher catalyst levels resulted in compounds with higher molar masses. Similar functional groups and distribution of chemical species were found by both FTIR and 13C-NMR spectroscopies in the hydrolysates of UFcured, indicating water hydrolysis of hydroxymethyl groups and then methylene linkages. Methylene linkages and mono- and tri-hydroxymethyl ureas were mainly responsible for the liberation of formaldehyde from UFcured during hydrolysis. The indicated compounds are believed to contribute to the long-term release of formaldehyde from the resins. This is the first systematic report on the composition of UFcured hydrolysates.

A 1H and 13C nuclear magnetic resonance study of carnosine

1986 ◽  
Vol 64 (11) ◽  
pp. 2132-2138 ◽  
Author(s):  
Jan O. Friedrich ◽  
Roderick E. Wasylishen
Keyword(s):  
Chemical Shifts ◽  
Imidazole Ring ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Basic Solution ◽  
Magnetic Resonance Study ◽  
Nmr Spectrum ◽  
13C Nuclear Magnetic Resonance ◽  
Nmr Techniques ◽  
C Nmr

The proton and carbon-13 resonance signals of carnosine (β-alanyl-L-histidine) were unambiguously assigned using a variety of nmr techniques including proton–carbon chemical shift correlations, titrations of nmr chemical shifts, coupling constants, and isotope shifts. From the 13C nmr titration, carnosine's three pKa values were estimated to be 2.7, 7.1, and 10.6, and it was found that the imidazole ring existed predominantly as the 3-H tautomer in basic solution. Conformational information about the Cα—Cβ bond and about the N—Cα bond was deduced from observed 3J(C,H) and 3J(H,H) values. The 13C nmr spectrum of carnosine in solution is also compared with that obtained for a solid sample.

scholarly journals Using 13C nuclear magnetic resonance spectroscopy for the study of northern hardwood tissues

2005 ◽  
Vol 35 (8) ◽  
pp. 1821-1831 ◽  
Author(s):  
Chris E Johnson ◽  
Ronald J Smernik ◽  
Thomas G Siccama ◽  
David K Kiemle ◽  
Zhihong Xu ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Structural Chemistry ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Betula Alleghaniensis ◽  
13C Nuclear Magnetic Resonance ◽  
Bark Chemistry ◽  
C Nmr ◽  
Nuclear Magnetic

Nuclear magnetic resonance (NMR) spectroscopy is a useful tool for examining the structural chemistry of natural organic matter. The use of cross-polarization and magic-angle spinning to study 13C functionality (CPMAS 13C NMR) is convenient, but not always quantitative. We used various 13C NMR techniques to examine the structural chemistry of bark and wood of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.), and yellow birch (Betula alleghaniensis Britt.). Spin counting experiments showed that 87%–97% of the 13C in the samples was observable by CPMAS 13C NMR. A comparison of CPMAS and Bloch decay experiments revealed few differences in spectral properties. Together, these results suggest that CPMAS 13C NMR is quantitative for these tissues. We observed little variation in the structural chemistry of wood, either among samples of the same species or among species. Within-species variations in bark chemistry were greater than in wood, probably because of variations in environmental conditions. However, we observed no significant differences in bark chemistry among the species. Bark and wood chemistry differed significantly, with the bark spectra displaying greater contributions from lignin, suberin, waxes, and resins. Hardwood spectra differ from softwood spectra in the aromatic C regions because of the contribution of syringyl units to hardwood lignin. Hardwood bark appears to contain less tannins than softwood bark. Together, the quantitative and qualitative features of CPMAS 13C NMR spectra are useful for studying the ecology of living and detrital wood and bark.

13C Nuclear magnetic resonance spectroscopy in the elucidation of structures of diterpenoid alkaloids

1987 ◽  
Vol 65 (1) ◽  
pp. 99-103 ◽  
Author(s):  
Balawant S. Joshi ◽  
John K. Wunderlich ◽  
S. William Pelletier
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Diterpenoid Alkaloids ◽  
Chemical Examination ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Nuclear Magnetic

13C Nuclear magnetic resonance spectroscopy is an exceptionally useful tool for the structure determination of diterpenoid alkaloids. A detailed study of the 1H and 13C nmr spectra of aconitine and 3-deoxyaconitine has permitted definite assignments to all the carbon atoms of the molecule. Chemical shift revisions have been suggested for certain carbon atoms of the C19-diterpenoid alkaloids. Chemical examination of Aconitumcolumbianum Nutt. ssp. columbianum, A. forrestii Stapf, Delphiniumtatsienense Franch., and D. vestitum Wall, resulted in the isolation of several new C19-diterpenoid alkaloids. The structure derivation of those alkaloids was based mainly on 13C nmr spectroscopic evidence.

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