Conformational Domino Effect in Saccharides: A Prediction from Alkyl β-(1→6)-Diglucopyranosides

详细信息    查看全文

• 作者：Alfredo Ro&#xeb ; n ; Juan I. Padró ; n ; Carlos Mayato ; Jesú ; s T. V&#xe1 ; zquez
• 刊名：Journal of Organic Chemistry
• 出版年：2008
• 出版时间：May 2, 2008
• 年：2008
• 卷：73
• 期：9
• 页码：3351 - 3363
• 全文大小：1226K
• 年卷期：v.73,no.9(May 2, 2008)
• ISSN：1520-6904

文摘

A series of alkyl β-D-glucopyranosyl-(1→6)-β-D-glucopyranosides, containing nonchiral and chiral aglycons, were synthesized and analyzed by NMR and CD. The results, collected from four sets of disaccharides, demonstrated that the rotational properties of the interglycosidic linkage depend on the structural natures of both the aglycon and the solvent. Stereoelectronic and steric factors explain this rotational dependence, the gauche−trans (gt) rotamer being the most stable. Furthermore, correlations between Taft’s steric parameters or between the pK_a values of the alkyl substituent (aglycon) versus corresponding rotamer populations were observed. These results point to a natural conformational domino effect in oligosaccharides, where the conformational properties of each (1→6) interglycosidic linkage will depend on the structure of the previous residue or its aglycon. In addition, a very weak rotational population dependence of the hydroxymethyl group at residue II on the aglycon at residue I was observed. The population of the gauche−gauche (gg) rotamer decreased, and that of gt increased as the Taft’s steric parameters of the remote aglycon increased, independently of the disaccharide series and of the solvent.