Formation of oxalo-substituted etheno derivatives in reactions of mucochloric acid with adenosine, guanosine and cytidine

Treatment of the nucleosides adenosine, guanosine and cytidine with mucochloric acid in slightly acid aqueous solutions at 37 °C affords oxalo-substituted etheno derivatives of nucleosides (2a, 3a and 4a). The derivatives are structurally characterised by UV, 1H and 13C NMR spectroscopy and mass spectrometry. In addition, all the long-range 1H–13C couplings are assigned in the base moieties of the products. A plausible mechanism is presented for the formation of the products.