Syntheses of [5‐2H]‐uracil, [5‐2H]‐cytosine, [6‐2H]‐uracil and [6‐2H]‐cytosine

Facile syntheses of [5-2H]-, [6-2H]-uracil and [5-2H]-, [6-2H]-cytosine were investigated. The catalytic reaction of uracil or cytosine with 2H2 gas in alkaline media gave rise to [6-2H]-compounds almost exclusively. On the other hand,the reaction of 5-bromouracil or 5-bromocytosine with 2H2 gas and gave rise to a mixture of [5-2H]-, [6-2H]- and [5-2H,6-2H]-compounds depending on the experimental conditions. By controlling the temperature, the pressure of 2H2 gas and the amounts of catalyst, [5-2H]-uracil and [5-2H]-cytosine were obtained. The isotopic distribution in each product was measured by 1H NMR spectroscopy combined with an HPLC method.