Thermal synthesis of nucleoside H-phosphonates under mild conditions.

Nucleosides react rapidly with ammonium phosphite ((NH4)2HPO3) at 60 degrees C to produce good yields of nucleoside-5'-phosphite monoesters within 24 h. Under the same conditions, ammonium phosphate is unreactive, producing low yields of nucleotide only after extended reactions. These results confirm earlier suggestions that nucleoside H-phosphonates and their possible condensation products may have been produced on the primitive earth more easily than nucleotides.