CONFIGURATIONAL EFFECTS IN THE PROTON MAGNETIC RESONANCE SPECTRA OF ACETYLATED CARBOHYDRATES<sup>1</sup>

Lemieux, R. U.; Kullnig, Rudolph K.; Bernstein, H. J.; Schneider, W. G.

doi:10.1021/ja01561a069

Cited by 113 publications

(18 citation statements)

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“…21 Nowadays, such equations are based on a multitude of experimental data and extensive Density Functional Theory (DFT) calculations at different levels of theory, which take bond lengths, electron densities, electron orbital terms, and dipolar electron spin terms into account. The observation of geometry-dependent coupling constants in six-membered rings and carbohydrates 22 has made Karplus equations especially useful to establish the conformation of the ring and the glycosidic bond. 23 Specifically, the glycosidic bond provides flexibility to the oligosaccharide and has great influence on the timeaveraged solution conformation of the glycan.…”

Section: Introductionmentioning

confidence: 99%

Structure assignment and H/D-exchange behavior of several glycosylated polyphenols

Franz¹,

Serebnitskaya²,

Gudial³

et al. 2014

Arkivoc

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The NMR-structures of six polyphenols, resveratrol (1), (-)-epicatechin (2), pelargonidin chloride (3), cyanidin chloride (4), cyanin chloride (5), and keracyanin chloride (6), were fully assigned. For the glycosylated polyphenols 5 and 6, the three-dimensional solution structure and long-range 1 H-13 C-coupling constants across the glycosidic bond were measured. Satisfactory fit to standard Karplus-equations was achieved for glycosides directly attached to the aromatic core in cyanin chloride. Molecular dynamics simulation data in vacuum at the AM1-level of theory were shown to approximate the NMR-solution data reasonably well. Selective HCl-catalyzed H/D-exchange was observed for aromatic protons H6 and H8 in flavonoid structures containing a 5,7-metadisubstituted chromelynium core with free OH-groups. The exchange took place readily in compounds 3, 4, and 6, whereas 1, 2, and 5 did not exchange.

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Section: Introductionmentioning

confidence: 99%

Structure assignment and H/D-exchange behavior of several glycosylated polyphenols

Franz¹,

Serebnitskaya²,

Gudial³

et al. 2014

Arkivoc

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“…(2). indicate a steric dependance analogous to that of H-H vicinal coupling in these colnpounds (3). The cun-ent study, which utilizes a vasiety of sugars and derivatives specifically labelled with carbon-1 3, f~~r n i s h e s a much more extensive description of orientational influences upon vicinal ' v -H coupling.'…”

mentioning

confidence: 99%

Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling

Schwarcz¹,

Perlin²

1972

Can. J. Chem.

162

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The effect of changes in the relative orientation of vicinal and geminal 13C and 1H nuclei, and in the disposition of adjacent substituents, on coupling between these nuclei has been examined with a variety of 13C-labelled carbohydrates. Compounds synthesized for this purpose include derivatives of D-glucose-1- and -6-13C and L-idose-6-13C, and related lactones, and the measurements have been made with p.m.r. spectra of these compounds. Vicinal 13C-1H coupling, both through C—C and C—O bonds shows an orientational dependance analogous to that for protons: i.e., dihedral angles of 60–100° are associated with smaller coupling (0–3 Hz) than angles of 140–180° (4.5–5.5 Hz); sp2 carbon produces splittings of almost twice these values. The observed spacing is smaller when an oxygen atom is in the plane of the coupling pathway than when out of plane, both for vicinal and geminal 13C–1H interactions, and the presence of an extra oxygen also may have a notable impact on the geminal interaction. A study of rotational isomerism in these compounds indicates that the characteristics of coupling between 13C and 1H nuclei may fruitfully be compared with those of H–H coupling in the analysis of such dynamic systems.

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“…Of the four possible arrangements of the glycol one, 2a,3/3, can be ilninediately dismissed since this would require a large trans diaxial coupling of the methine protons (J --8-10 c.p.s.) (20) whereas that observed is -3.8 c.p.s. Of those remaining only the 2a, 3a, and 2P,3P would be expected t o give an isopropylidene derivative easily (21).…”

Section: Hooc )mentioning

confidence: 57%

Terpenoids: V. Senegenin: Functional Groups and Part Structure

Dugan¹,

Mayo²,

Starratt³

1964

Can. J. Chem.

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Senegenin, the sapogenin from Polygala senega has been shown to contain chlorine; it has the empirical formula C30H4506Cl. The oxygen atoms, contrary to earlier work, are contained in two carboxyl groups and two secondary hydroxyl groups. There is one isolated ethylenic linkage. The environment of the hydroxylic functions and one carboxyl group has been shown t o be as in (XI).Of the known triterpenoids of undetermined constitution remaining, senegenin has a claim to outstanding interest. Investigations directed to a study of the saponin of Polygala senega have spread over many years, but, as mentioned by Simonsen and Ross (I), such "investigations. . . have given rise to very divergent results". I t is this confusion, and its present clarification, which exculpates us from a charge of literary proiiferation in the presentation of incomplete work.Although senega extract has been used medicinally for some time, chiefly as a n expectorant (however, see ref.2 ) , the first results of chemical importance were obtained by Wedekind and Krecke (3). They isolated, by acid hydrolysis of the saponin, a product to which they assigned the formula C26H4406. I t contained two hydroxyl groups, as indicated by the formation of a diacetate, and gave a dimethyl ester.A more extensive study was later reported by Jacobs and Isler (4), who observed the presence of two crystalline sapogenins. T h a t of bwer solubility appeared to be senegenin, although the constants differed somewhat from those of Wedekind and Krecke: the diacetate, in particular, melted a t a much higher temperature. The empirical formula C30H4608 or C30H4408 was proposed, and evidence for an isolated ethylenic linkage found in a weak tetranitromethane test. Titration with alkali indicated the presence of two carboxyl groups (again confirmed by the preparation of a non-crystalline dimethyl ester) and the presence of a lactone was inferred by the consumption of a third equivalent of alkali on heating. Senegenin could not be recovered from the acidified hydrolysis mixture.The second sapogenin isolated from senega root by Jacobs and Isler was an acid, m.p. 257", which appeared to have the empirical formula C31H.5006 or C31H4806. This substance also gave a positive reaction with tetranitromethane, and was shown to give a diacetate. Hydrolysis revealed it to be the monoethyl ester of a dibasic acid. Both the sapogenins gave, on selenium dehydrogenation, the same substituted picene obtained previously from such triterpenoids as oleanolic acid, and shown to be ( 5 ) 1,8-dimethylpicene: results which strongly supported the supposition of Jacobs and Isler that they were dealing with a triterpenoid.

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CONFIGURATIONAL EFFECTS IN THE PROTON MAGNETIC RESONANCE SPECTRA OF ACETYLATED CARBOHYDRATES¹

Cited by 113 publications

References 0 publications

Structure assignment and H/D-exchange behavior of several glycosylated polyphenols

Structure assignment and H/D-exchange behavior of several glycosylated polyphenols

Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling

Terpenoids: V. Senegenin: Functional Groups and Part Structure

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CONFIGURATIONAL EFFECTS IN THE PROTON MAGNETIC RESONANCE SPECTRA OF ACETYLATED CARBOHYDRATES1

Cited by 113 publications

References 0 publications

Structure assignment and H/D-exchange behavior of several glycosylated polyphenols

Structure assignment and H/D-exchange behavior of several glycosylated polyphenols

Orientational Dependance of Vicinal and Geminal 13C–1H Coupling

Terpenoids: V. Senegenin: Functional Groups and Part Structure

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CONFIGURATIONAL EFFECTS IN THE PROTON MAGNETIC RESONANCE SPECTRA OF ACETYLATED CARBOHYDRATES¹

Orientational Dependance of Vicinal and Geminal ¹³C–¹H Coupling