Unambiguous structural elucidation of base‐modified purine nucleosides using NMR

Abstract

A general and unambiguous approach has been developed for structural elucidation of modified purine nucleosides using NMR spectroscopy. Systematic assignment of proton and carbon signals of modified nucleosides was firmly established by COSY and the anomerism of the glycosidic linkage of synthetic nucleosides clearly elucidated by NOESY experiments. Characteristic properties of 15N-isotopic labelling at specific positions of nucleosides were also employed for structural studies. The reported approach is applicable to other modified nucleosides and nucleotides, as well as nucleobases.

Systematic assignment of NMR spectra of 5‐substituted‐4‐thiopyrimidine nucleosides

“…By comparison with the reported data for un‐modified nucleosides, we can be confident that the chemical shifts of all the sugar protons would be below 6 ppm (Table ). The protons of the sugar OHs can be readily identified by the means of D 2 O exchanges.…”

“…This has prompted us to carry out a systematic NMR examination of nucleosides, in particular, base‐modified nucleosides. Previously, we reported an unambiguous approach to determining structures of purine‐modified deoxynucleosides . Recently, we extended our work to some 4‐thiopyrimidine deoxynucleosides .…”

“…Here, we take 5‐bromo‐4‐thiopyrimidine ribonucleoside ( 4e ) as an example to illustrate a general approach to the NMR study of pyrimidine‐modified nucleosides. Together with our early work on purine‐modified nucleosides, we can offer a complete 1 H and 13 C NMR assignments for both purine‐modified and pyrimidine‐modified nucleosides and clarify some inconsistent NMR assignments in the literature.…”

“…Previously, we reported an unambiguous approach to determining structures of purine-modified deoxynucleosides. [13] Recently, we extended our work to some 4thiopyrimidine deoxynucleosides. [14] With the availability of all 5halogenated-4-thionucleosides (ribo and deoxyribo), we were able to carry out a systematic and comparable NMR study of both types of nucleosides.…”

Nonpeptide small molecules from the insect Aspongopus chinensis and their neural stem cell proliferation stimulating properties

“…By comparison of their spectroscopic data to those of the previously reported substances, these natural products were shown to be aspongopusin (10), 2 nicodine (11), 5 2-quinolinol (12) 28 and thymidine (37). By comparison of their spectroscopic data to those of the previously reported substances, these natural products were shown to be aspongopusin (10), 2 nicodine (11), 5 2-quinolinol (12) 28 and thymidine (37).…”