Dependence of Pyranose Ring Puckering on Anomeric Configuration: Methyl Idopyranosides

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• 作者：Benedict M. Sattelle ; Bidisha Bose-Basu ; Matthew Tessier ; Robert J. Woods ; Anthony S. Serianni ; Andrew Almond
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：June 7, 2012
• 年：2012
• 卷：116
• 期：22
• 页码：6380-6386
• 全文大小：385K
• 年卷期：v.116,no.22(June 7, 2012)
• ISSN：1520-5207

文摘

In the aldohexopyranose idose, the unique presence of three axial ring hydroxyl groups causes considerable conformational flexibility, rendering it challenging to study experimentally and an excellent model for rationalizing the relationship between puckering and anomeric configuration. Puckering in methyl 伪- and 尾-l-idopyranosides was predicted from kinetically rigorous 10 渭s simulations using GLYCAM11 and three explicit water models (TIP3P, TIP4P, and TIP4P-EW). In each case, computed pyranose ring three-bond (vicinal) ¹H鈥?sup>1H spin couplings (³J_H,H) trended with NMR measurements. These values, calculated puckering exchange rates and free energies, were independent of the water model. The 伪- and 尾-anomers were ¹C₄ chairs for 85 and >99% of their respective trajectories and underwent ¹C₄鈫?sup>4C₁ exchange at rates of 20 渭s^鈥? and 1 渭s^鈥?. Computed 伪-anomer ¹C₄鈫?sup>4C₁ puckering rates depended on the exocyclic C6 substituent, comparing hydroxymethyl with carboxyl from previous work. The slower kinetics and restricted pseudorotational profile of the 尾-anomer were caused by water occupying a cavity bounded by the anomeric 1-O-methyl and the C6 hydroxymethyl groups. This finding rationalizes the different methyl 伪- and 尾-l-idopyranoside ³J_H,H values. Identifying a relationship between idopyranose anomeric configuration, microsecond puckering, and water structure facilitates engineering of biologically and commercially important derivatives and underpins deciphering presently elusive structure鈥揻unction relationships in the glycome.