13C−13C NMR Spin−Spin Coupling Constants in Saccharides:  Structural Correlations Involving All Carbons in Aldohexopyranosyl Rings

• Published in: Journal of organic chemistry Vol. 72; no. 20; pp. 7511 - 7522
• Main Authors: Bose-Basu, Bidisha, Klepach, Thomas, Bondo, Gail, Bondo, Paul B, Zhang, Wenhui, Carmichael, Ian, Serianni, Anthony S
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 28.09.2007
• Subjects: Carbohydrate Conformation; Carbohydrates with 4, 5, 6, ... C atoms, dissacharides and oligosaccharides; Carbohydrates. Nucleosides and nucleotides; Carbon Isotopes; Chemistry; Exact sciences and technology; Glycosides - chemistry; Models, Molecular; Nuclear Magnetic Resonance, Biomolecular - methods; Oligosaccharides - chemistry; Organic chemistry; Preparations and properties; Substituent effect; Spin spin coupling constant; Correlation; Configuration; Molecular structure; Oligosaccharide; Prediction; Theoretical study; Oside; NMR spectrometry; Geminal compound; Anomer; Density functional method; Glycoside; Carbon 13; Labelled compound
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo0706776

13C−13C Spin−spin coupling constants (J CC) 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 J CC magnitude and sign and saccharide structure. Structural correlations for 2 J C1,C3, 2 J C 2,C4, 2 J C4,C6, and 2 J C1,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 2 J CCC values are also affected by intervening carbon structure and C−O bond rotation. 3 J C1,C6 and 3 J C3,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. 3 J C3,C6 is also affected by C4 configuration. Both 3 J C1,C6 and 3 J C3,C6 are subject to remote effects involving the structure at C3 and C1, respectively. New structural correlations have been determined for 2 J C3,C5, which, like 3 J C3,C6, shows a remote dependence on anomeric configuration. Investigations of dual pathway 13C−13C couplings, 3+3 J C1,C4 and 3+3 J C 2,C5, revealed an important additional internal electronegative substituent effect on 3 J CC in saccharides, a structural factor undocumented previously and one of importance to the interpretation of trans-glycoside 3 J COCC in oligosaccharides.