Nuclear magnetic resonance spectroscopy. Carbon-13 spectra of some pentose and hexose aldopyranoses

Abstract

Natural-abundance 13C spectra of selected pentose and hexose aldopyranoses are reported and discussed. The 13C chemical shifts of these substances are shown to be heavily dependent upon the proximity of the substituents on the pyranose ring. Variousinvestigations3-5 have evinced the utility of (9) F.

Glycosides from Muscaricomosum. 4. Structure of muscaroside A

“…, .~.~ of the arabinose unit falls in a range which has often been taken as an indication of a-configuration (17,18). More recently, however, the value of this coupling constant, as well as J;.,,,.,, has been reported (19) not to be diagnostic on its own, owing to the high conformational mobility of arabinopyranosides ( T I @ 'C,) (20). Finally, shift values (6 66.5 and 6 64.2) attributed (Table 1, Py-d,) to A-4 and A-5, respectively, accorded neither with the corresponding values (6 69.1 and 6 66.6, respectively) given for reference methyl a-L-arabinopyranoside nor with the values (6 70.8 and 6 63.9, respectively) given (21) for methyl P-L-arabinopyranoside.…”

Aspects of the chemistry of glycosides

“…Although a-and ß-anomers in this series may exhibit chemical shifts that are too similar for easy differentiation (Refs. 25,26), their configuration may be assigned confidently on the basis of 1~-l H-l measurements. That is, in common with various diastereemers (Refs.…”

Molécules modèles des motifs des poly-1,4-glucosides. I. Synthèse et correspondance configurationelle de diastéréoisomères avec les motifs de la cellulose et de l'amylose

“…AEu dCsigne les diffirences observCes entre les dkplacements chimiques mesurCs en prCsence et en absence de (DPM),Eu dans le benzene deutCriC, extrapolCes pour des rapports molaires (DPM),-Eu: solutC Cgaux a 1 (45,46). Les natures des diffkrentes contraintes stCriques permettant d'attribuer les 13C tktrahydropyranniques et cyclohexa-; niques, ont Ct C dCterminCes en fonction des valeurs 1 des diplacements de signaux (47)(48)(49)(50)(51)(52).…”

“…Observations et attributions effectuks a partir du spectre rmn I3C du compose 1. La nature des diffkrentes contraintes stkriques a ete determinee sur la base des risultats bibliographiques (50)(51)(52)(53) et les references spectrales sont le diplacement chimique du cyclohexane (6 27.6 ppm) pour les 13C de type cyclohexanique et ceux du tktrahydropyranne (68.8, 27.4 et 24.3 ppm) pour les 13C tetrahydropyranniques d'une interpretation plus dtlicate en ce qui concerne leurs attributions, en raison de la prtsence simultante de deux fonctions alcool sur le squelette cyclohexyloxy-2 tttrahydropyrannique. De plus, il n'est pas significatif, dans ce cas, d'enregistrer les spectres en prtsence de sels d'europium, ainsi que nous l'avons signal6 prtctdemment.…”