Bose-Basu Bidisha, Klepach Thomas, Bondo Gail, Bondo Paul B, Zhang Wenhui, Carmichael Ian, Serianni Anthony S
Department of Chemistry and Biochemistry and Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA.
J Org Chem. 2007 Sep 28;72(20):7511-22. doi: 10.1021/jo0706776. Epub 2007 Sep 7.
13C-13C Spin-spin coupling constants (JCC) have been measured in a group of aldohexopyranoses and methyl aldopyranosides singly labeled with 13C at different sites to confirm and extend prior correlations between JCC magnitude and sign and saccharide structure. Structural correlations for 2JC1,C3, 2JC2,C4, 2JC4,C6, and 2JC1,C5 have been confirmed using density functional theory calculations to test empirical predictions. These geminal couplings depend highly on the orientation of C-O bonds appended to the terminal coupled carbons, but new evidence suggests that 2JCCC values are also affected by intervening carbon structure and C-O bond rotation. 3JC1,C6 and 3JC3,C6 values show Karplus-like dependences but also are affected by in-plane terminal hydroxyl substituents. In both cases, rotation about the C5-C6 bond modulates the coupling due to the alternating in-plane and out-of-plane O6. 3JC3,C6 is also affected by C4 configuration. Both 3JC1,C6 and 3JC3,C6 are subject to remote effects involving the structure at C3 and C1, respectively. New structural correlations have been determined for 2JC3,C5, which, like 3JC3,C6, shows a remote dependence on anomeric configuration. Investigations of dual pathway 13C-13C couplings, 3+3JC1,C4 and 3+3JC2,C5, revealed an important additional internal electronegative substituent effect on 3JCC in saccharides, a structural factor undocumented previously and one of importance to the interpretation of trans-glycoside 3JCOCC in oligosaccharides.
已在一组在不同位点单标记有¹³C的己醛吡喃糖和甲基醛吡喃糖苷中测量了¹³C-¹³C自旋-自旋耦合常数（JCC），以确认并扩展先前关于JCC大小和符号与糖类结构之间的相关性。使用密度泛函理论计算来检验经验预测，已证实了²J C1,C3、²J C2,C4、²J C4,C6和²J C1,C5的结构相关性。这些偕偶耦合高度依赖于连接到末端耦合碳上的C-O键的取向，但新证据表明²JCCC值也受中间碳结构和C-O键旋转的影响。³J C1,C6和³J C3,C6值呈现类似Karplus的依赖性，但也受面内末端羟基取代基的影响。在这两种情况下，围绕C5-C6键的旋转由于O6在面内和面外的交替而调节耦合。³J C3,C6也受C4构型的影响。³J C1,C6和³J C3,C6都分别受到涉及C3和C1处结构的远程效应的影响。已确定了²J C3,C5的新结构相关性，它与³J C3,C6一样，显示出对异头构型的远程依赖性。对双途径¹³C-¹³C耦合³ + ³J C1,C4和³ + ³J C2,C5的研究揭示了糖类中³JCC上一个重要的额外内部电负性取代基效应，这是一个以前未记录的结构因素，对解释寡糖中的反式糖苷³JCOCC很重要。
