Selective transcription of an unnatural naphthyridine:imidazopyridopyrimidine base pair containing four hydrogen bonds with T7 RNA polymerase.

The naphthyridine:imidazopyridopyrimidine base pair is the first base pair containing four hydrogen bonds that can be replicated selectively and efficiently by the use of DNA polymerases. Herein we describe the synthesis of naphthyridine-C-ribonucleoside 5'-triphosphate (rNaTP) and transcription reactions catalyzed by T7 RNA polymerase with rNaTP and template DNA containing imidazopyridopyrimidine. The transcription reaction was also applied to a longer transcript containing part of the human c-Ha-Ras gene.