Purine nucleobases are essential building blocks of DNA and RNA, which provide important binding sites in nucleic acids. They are excellent ligands for metal ions and usually form Werner-type complexes using the N-donor atoms of the nucleobase skeleton. Most recently, the regioselective C-metalation of purines such as caffeine and 9-methyladenine has been reported, which are rare examples of a C8-metalated purine nucleobase synthesized by oxidative addition. Here we show that not only free purine nucleobases can be C8-metalated but also nucleosides (nucleobase + pentose) such as adenosine and guanosine. For the oxidative addition the introduction of a C–X bond as well as the protection of the hydroxyl groups (here by acetylation) is essential. The purine nucleobase reacts selectively at the C8-position with metal precursors such as [M0(PPh3)4], followed by N-protonation, to form novel chiral C8-metalated nucleoside NHC metal complexes (Figure 1).

Selective C8-metalation of various purine nucleosides

253rd National Meeting (2017)

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