Figure 1.

Characterization and assignment of the TBDMS isomers via HSQC (red) and HMBC (blue) NMR measurements. A) The merged ¹H signal at 5.17 ppm results from the H2’ and an OH group, since the H3’ can be clearly identified through the HMBC correlation with C5’. The zoomed region shows the HMBC correlation of the OH group with C4’, which together with the weaker signal between H2’ and C1’ identifies this nucleoside as the 2’-O-TBDMS isomer. B) The H3’-signal is distinct from the H3’ signal in A in its multiplicity, and the OH group has a HMBC correlation with C1’, not with C4’, which identifies this nucleoside as the 3’-O-TBDMS isomer.