Convenient syntheses of isotopically labeled pyrimidine 2'-deoxynucleosides and their 5-hydroxy oxidation products.

Hydrolytic and oxidative damage to pyrimidine nucleobases in DNA represents a significant source of mutations in the human genome. To better understand how these lesions are incorporated and repaired in human cells, it is desirable to have ready access to isotopically enriched nucleosides for use in isotope tracing and mass spectrometry-based quantification experiments. Here we report on improved syntheses of deoxyuridine, deoxycytidine, 5-hydroxydeoxyuridine, and 5-hydroxydeoxycytidine nucleosides labeled with ¹³C and ¹⁵N. Deoxyuridine was synthesized from uracil in a direct glycosylation reaction with excellent stereoselectivity without the need to reduce a ribonucleoside intermediate. Deoxyuridine was further converted to deoxycytidine using mild O4 activation conditions with high efficiency. Finally, we document the synthetic details of preparative oxidation of deoxyuridine and deoxycytidine to their 5-hydroxy counterparts. Overall, our protocols avoid hazardous reagents and tedious conditions found in previous methods.