Table 5. Summary of All RNA Phosphoramidite Labels As Outlined in Schemes 15–22.
| RNA phosphoramidite labela | time (days)b | chemical stepsc | yield (%) | ref |
|---|---|---|---|---|
| [8-13C]-N6-Bz-adenosine (TOM) | 4.5 | 5 (4) | 17 | (85) |
| [2,8-13C2]-N6-methyladenosine (tBDMS) | 8 | 11 (5) | 4 | (149) |
| [8-13C]-N2-Ac-guanosine (TOM) | 5 | 5 (4) | 18 | (85) |
| [6-13C, 5-2H]-N4-Ac-cytidine (TOM) | 8 | 8 (6) | 34 | (85) |
| [5-13C, 5-19F]-N4-Ac-cytidine (tBDMS) | 10 | 8 (6) | 4 | (57) |
| [6-13C, 5-2H]-uridine (TOM) | 4 | 5 (3) | 22 | (85) |
| [5-13C, 5-19F]-uridine (tBDMS) | 7.5 | 6 (4) | 8 | (57) |
| [1,3-15N2]-cmo5-uridine (tBDMS) | 8 | 15 (3) | 1 | (148) |
a
The 2′-OH protecting groups are listed in the parentheses.
b
Total reaction time was based on the time required for all chemical steps. In addition, 16 h were added for any explicit mention of overnight procedures and 24 h were added for any chromatographic purifications.
c
Reactions for amidites harboring post-transcriptional modifications begin with isotope-labeled precursors whereas reactions for unmodified amidites begin with isotope-labeled protected nucleobase. Also, the number in parentheses represents the number of chromatographic purification steps.