Table 3.
Selected chemical shifts of the three ribosides of εisoGua. Chemical shift labels follow the naming convention of IUPAC-IUBMB-IUPAB [35], extended for the etheno protons (see Scheme 1). NA – resonance not assigned. For the N7- and N9-ribosides, atoms in the positions 10 and 11 could not be unequivocally differentiated, and the two possible values are slash-separated.
| Atom | Sample/Chemical Shift (PPM) | ||
|---|---|---|---|
| N6-riboside | N7-riboside | N9-riboside | |
| H1’ | 6.511 | 5.987 | 5.712 |
| H8 | 7.822 | 8.262 | 7.753 |
| H10 * | 7.775 | 7.301/7.79 | 7.212/7.520 |
| H11 ** | 7.827 | ||
| C1’ | 90.293 | 89.833 | 89.114 |
| C5 | NA | 104.600 | NA |
| C6 | 138.682 | 137.918 | 141.788 |
| C8 | 137.799 | 140.026 | 135.525 |
| C10 | 113.386 | 130.645/113.699 | NA/111.558 |
| C11 | 116.951 | ||
* H7 or C7 according to IUPAC notation; ** H8 or C8 according to IUPAC notation.