1,7-Dioxaspiro[5.5]undecanes. An excellent system for the study of stereoelectronic effects (anomeric and exo-anomeric effects) in acetals

1981 ◽  
Vol 59 (7) ◽  
pp. 1105-1121 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Daryl D. Rowan ◽  
Normand Pothier ◽  
Gilles Sauvé ◽  
John K. Saunders
Keyword(s):  
Experimental Results ◽  
Nmr Analysis ◽  
Steric Interactions ◽  
Stereoelectronic Effects ◽  
Anomeric Effects ◽  
Acid Cyclization ◽  
C Nmr

Several isomeric compounds derived from the spiro systems 5 to 9 (Scheme 4) were obtained from the acid cyclization of the appropriate dihydroxy ketone precursor.The configuration and the conformation of the products obtained was determined by 13C nmr analysis and equilibration studies. The experimental results can be rationalized by taking into account the anomeric and the exo-anomeric effects and the usual steric interactions.

1,7-Dithia and 1-oxa-7-thiaspiro[5.5]undecanes. Excellent systems for the study of stereoelectronic effects (anomeric and exo-anomeric effects) in the monothio and the dithioacetal functions

1981 ◽  
Vol 59 (7) ◽  
pp. 1122-1131 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Daryl D. Rowan ◽  
Normand Pothier ◽  
John K. Saunders
Keyword(s):  
Experimental Results ◽  
Hydroxy Ketone ◽  
Nmr Analysis ◽  
Steric Interactions ◽  
Stereoelectronic Effects ◽  
Anomeric Effects ◽  
Acid Cyclization ◽  
C Nmr

1,7-Dithiaspiro[5.5]undecane (2), 1-oxa-7-thiaspiro[5.5]undecane (4), and the tricyclic systems 3, 5, and 6 have been prepared by the acid cyclization of the appropriate ketone dithiol or hydroxy ketone thiol precursors.The configuration and the conformation of the products obtained was determined by 13C nmr analysis and equilibration studies. The experimental results can be rationalized by taking into account the anomeric and the exo-anomeric effects and the usual steric interactions.

Synthesis and Structure Assignment of 2-(4-Methoxybenzyl)cyclohexyl β-D-Glucopyranoside Enantiomers

2006 ◽  
Vol 71 (10) ◽  
pp. 1470-1483 ◽  
Author(s):  
David Šaman ◽  
Pavel Kratina ◽  
Jitka Moravcová ◽  
Martina Wimmerová ◽  
Zdeněk Wimmer
Keyword(s):  
Analytical Data ◽  
Chiral Hplc ◽  
Nmr Analysis ◽  
Target Structure ◽  
Enantiomerically Pure ◽  
Whole Cells ◽  
H Nmr ◽  
Structure Assignment ◽  
Related Compounds ◽  
C Nmr

Glucosylation of the cis- and trans-isomers of 2-(4-methoxybenzyl)cyclohexan-1-ol (1a/1b, 2a/2b, 1a or 2a) was performed to prepare the corresponding alkyl β-D-glucopyranosides, mainly to get analytical data of pure enantiomers of the glucosides (3a-6b), required for subsequent investigations of related compounds with biological activity. One of the employed modifications of the Koenigs-Knorr synthesis resulted in achieving 85-95% yields of pure β-anomers 3a/3b, 4a/4b, 3a or 4a of protected intermediates, with several promoters and toluene as solvent, yielding finally the deprotected products 5a/5b, 6a/6b, 5a or 6a as pure β-anomers. To obtain enantiomerically pure β-anomers of the target structure (3a, 4a, 5a and 6a) for unambiguous structure assignment, an enzymic reduction of 2-(4-methoxybenzyl)cyclohexan-1-one by Saccharomyces cerevisiae whole cells was performed to get (1S,2S)- and (1S,2R)-enantiomers (1a and 2a) of 2-(4-methoxybenzyl)cyclohexan-1-ol. The opposite enantiomers of alkyl β-D-glucopyranosides (5b and 6b) were obtained by separation of the diastereoisomeric mixtures 5a/5b and 6a/6b by chiral HPLC. All stereoisomers of the products (3a-6b) were subjected to a detailed 1H NMR and 13C NMR analysis.

scholarly journals Biosynthesis of Isoflavonoid Phytoalexins: Incorporation of Sodium [1,2-13C2] Acetate into Phaseollin and Kievitone

1982 ◽  
Vol 37 (5-6) ◽  
pp. 363-368 ◽  
Author(s):  
Paul M. Dewick ◽  
Melanie J. Steele ◽  
Richard A. Dixon ◽  
Ian M. Whitehead
Keyword(s):  
Phaseolus Vulgaris ◽  
Nmr Analysis ◽  
Polyketide Chain ◽  
C Nmr

Abstract13C-NMR analysis of the isoflavonoid phytoalexins phaseollin and kievitone produced by feeding sodium [1,2-13C2]acetate to wounded bean (Phaseolus vulgaris) cotyledons has demonstrated the incorporation of intact acetate units into the aromatic A rings. Phaseollin shows a specific folding of the polyketide chain, whereas kievitone exhibits a randomisation of label in accordance with the intermediacy of a 2′,4′,6′-trihydroxylated chalcone during its formation. In neither case was sufficient label incorporated into analysis.

scholarly journals Noninvasive Measurement of Murine Hepatic Acetyl-CoA13C-Enrichment Following Overnight Feeding with13C-Enriched Fructose and Glucose

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Filipa Carvalho ◽  
Joao Duarte ◽  
Ana Rita Simoes ◽  
Pedro F. Cruz ◽  
John G. Jones
Keyword(s):  
Drinking Water ◽  
Benzoic Acid ◽  
Noninvasive Measurement ◽  
Nmr Analysis ◽  
Acetyl Coa ◽  
Normal Chow ◽  
A Minor ◽  
Pyruvate Recycling ◽  
Amino Benzoic Acid ◽  
C Nmr

The13C-isotopomer enrichment of hepatic cytosolic acetyl-CoA of overnight-fed mice whose drinking water was supplemented with [U-13C]fructose, and [1-13C]glucose andp-amino benzoic acid (PABA) was quantified by13C NMR analysis of urinaryN-acetyl-PABA. Four mice were given normal chow plus drinking water supplemented with 5% [1-13C]glucose, 2.5% [U-13C]fructose, and 2.5% fructose (Solution 1) overnight. Four were given chow and water containing 17.5% [1-13C]glucose, 8.75% [U-13C]fructose and 8.75% fructose (Solution 2). PABA (0.25%) was present in both studies. UrinaryN-acetyl-PABA was analyzed by13C NMR. In addition to [2-13C]- and [1,2-13C]acetyl isotopomers from catabolism of [U-13C]fructose and [1-13C]glucose to acetyl-CoA, [1-13C]acetyl was also found indicating pyruvate recycling activity. This precluded precise estimates of [1-13C]glucose contribution to acetyl-CoA while that of [U-13C]fructose was unaffected. The fructose contribution to acetyl-CoA from Solutions 1 and 2 was 4.0 ± 0.4% and 10.6 ± 0.6%, respectively, indicating that it contributed to a minor fraction of lipogenic acetyl-CoA under these conditions.

Mechanistic Aspects of Polynaphthalimide Synthesis from NMR Analysis

2009 ◽  
Vol 21 (5) ◽  
pp. 624-632 ◽  
Author(s):  
Fabienne Piroux ◽  
Regis Mercier ◽  
Dominique Picq
Keyword(s):  
Model Compound ◽  
Intermediate Compound ◽  
Polycondensation Reaction ◽  
Nmr Analysis ◽  
C Nmr

The mechanism of the polycondensation reaction leading to naphthalimide polymers has been investigated using a model compound. In complement to 19F-NMR analysis, 1H- and 13C-NMR spectroscopies were used to identify the intermediate compound. It was concluded that there was no evidence for the formation of an isoimide, but the formation of an amide—acid intermediate was clearly demonstrated.

Oxidative coupling of naphtho-9-crown-3 ether: X-ray crystal structure and solution and solid-state NMR analysis of the dimer

2001 ◽  
Vol 79 (10) ◽  
pp. 1505-1510 ◽  
Author(s):  
G W Buchanan ◽  
M F Rastegar ◽  
G PA Yap ◽  
A Moghimi ◽  
M Ghandi
Keyword(s):  
Solid State ◽  
Oxidative Coupling ◽  
Solid State Nmr ◽  
Nmr Analysis ◽  
Oxidative Dimerization ◽  
Nmr Spectrum ◽  
X Ray ◽  
Nmr Data ◽  
Group A ◽  
C Nmr

Treatment of naphtho-9-crown-3 ether with FeCl3 and aqueous H2SO4 generates bis-naphtho-9-crown-3 ether in ca. 30% yield. This compound crystallizes in the monoclinic P21/n space group; a = 9.2004(9), b = 18.0868(17), and c = 13.2078(13) Å, β = 97.799(2)° and Z = 4. 1H and 13C NMR data have been obtained in solution, and the solid-state 13C NMR spectrum is included for comparison. A chemical shift range of ca. 12 ppm has been found for the oxygenated aliphatic carbons in the solid state, in contrast to the 3 ppm range in the solution 13C NMR spectrum. These results are discussed in terms of the torsional environments of the carbon sites in the crystal structure.Key words: crown ether, stereochemistry, oxidative dimerization.

Solution carbocation stabilities measured by internal competition for a hydride ion

1982 ◽  
Vol 60 (17) ◽  
pp. 2180-2193 ◽  
Author(s):  
Nancy E. Okazawa ◽  
Ted S. Sorensen
Keyword(s):  
Nmr Spectroscopy ◽  
Equilibrium Constants ◽  
Analytical Tool ◽  
Steric Interactions ◽  
Hydride Ion ◽  
Methylene Chain ◽  
Internal Competition ◽  
Equilibration Process ◽  
Better Than ◽  
C Nmr

Although many techniques are known which allow one to compare the stabilities of solution carbocations, that involving the intermolecular competition for a hydride ion is conceptually (but not experimentally) the simplest procedure. This paper describes a variant of this which is experimentally more reliable and which uses intramolecular equilibria where the two competing systems are held together by a —(CH2)n— chain, e.g.[Formula: see text]By systematically varying "n" in this example (n = 0, 1,2, or 3), it has been found that a methylene chain of two or more carbons is necessary in order to minimize steric interactions between the end "systems". It has also been found that all cycloalkyl rings studied (except cyclohexyl) stabilize a cation centre much better than an aliphatic equivalent, i.e. [Formula: see text], in agreement with solvolysis rate studies. The same situation was found when comparing this aliphatic "system" against the 2-norbornyl cation (bicyclic) or against the tricyclic 2-adamantyl cation. In fact, in these cases the equilibria are too lop-sided to obtain numerical values for the equilibrium constants concerned. Finally, three carbocations were looked at where the 2-norbornyl cation structure was pitted against the structurally very related cyclopentyl, bicyclo[2.1.1]hexyl, and bicyclo[3.2.1]octyl cations. In all cases, the 2-norbornyl cation is the more stable. 13C nmr spectroscopy was used as the analytical tool to measure (or attempt to measure) the equilibrium constants. Depending on the rate of the equilibration process, three different techniques are involved and the relative merits of these are discussed in the latter part of the paper.

scholarly journals Kernresonanzspektroskopische Untersuchungen an t-Butyl-phenyl-phosphinsäure-(—)-menthylester, II [1]1H-, 13C-und 31P-NMR-Analyse der absoluten Konfiguration am Phosphoratom / NMR Spectroscopic Investigations on t-Butyl-phenyl-phosphinic Acid(—)-Menthyl Ester, II [1] 1H, 13C and 31P NMR Analysis of Absolute Configuration at the Phosphorus Center

1980 ◽  
Vol 35 (10) ◽  
pp. 1182-1190 ◽  
Author(s):  
Gerhard Hägele ◽  
Detlef Wendisch ◽  
Reiner Luckenbach ◽  
Hans-H. Bechtolsheimer
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
31P Nmr ◽  
Double Resonance ◽  
Phosphinic Acid ◽  
Nmr Analysis ◽  
Spectroscopic Investigations ◽  
Phosphinic Acids ◽  
13C And 31P Nmr ◽  
C Nmr

Abstract(-)-Menthol, Diastereomeric Menthylesters of Phosphinic Acids, 31P NMR Spectra, 13C NMR Spectra, Double Resonance(-)-Menthol and diastereomeric (-)-menthyl esters of t-butyl-phenyl-phosphinic acid are investigated by means of 1H, 13C and 31P NMR at 2.1 and 8.4. Tesla double resonance experiments are described.

Further Studies on the Biosynthesis of Granaticin

1986 ◽  
Vol 41 (1-2) ◽  
pp. 215-221 ◽  
Author(s):  
Xian-guo He ◽  
Chiu-Chin Chang ◽  
Ching-jer Chang ◽  
John C. Vederas ◽  
A. Gavin M clnnes ◽  
...  
Keyword(s):  
Triple Resonance ◽  
Triple Resonance Nmr ◽  
Nmr Analysis ◽  
Pyran Ring ◽  
Shift Method ◽  
Biosynthetic Precursor ◽  
C Nmr

Abstract Experiments with cerulenin-inhibited cultures of 5. violaceoruber showed conversion of dihydrogranaticin (II) into granaticin (I), but not vice versa, confirming an earlier conclusion that II is the biosynthetic precursor of I. Feeding of CH313C18O2Na followed by 13C-NMR analysis of the product by the 18O shift method indicated the expected incorporation of 18O at carbons 1,11 and 13 of I and showed that the oxygen of the pyran ring originates from C-3 and not from C-15. Analysis of I biosynthesized from 13C2H3COONa by 13C{1H, 2H} triple resonance NMR spectro­scopy showed the incorporation of one atom of deuterium each at C-2 and C-4. C-16 carried a maximum of 2, not 3, atoms of deuterium. These results are discussed in terms of biosynthetic mechanisms.

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