I. Hirao et al., Synthesis of DNA templates containing the fifth base, 2-amino-6-(dimethylamino)purine, for specific transcription involving unnatural base pairs, CHEM LETT, (9), 2001, pp. 914-915
An unnatural nucleobase, pyridin-2-one (denoted as y), can be specifically
incorporated into RNA opposite 2-amino-6-(dimethylamino)purine (denoted as
x) in DNA templates by T7 RNA polymerase. For the easy preparation of DNA t
emplates containing x, protecting groups for the 2-amino group of x were ex
amined. Although the general N2 protecting groups, such as isobutyryl and a
cetyl, resisted removal by the usual treatment with concentrated ammonia at
55 degreesC for 6 h, the N2-phenoxyacetyl group was successfully removed f
rom the protected oligomers. This DNA synthesis would be a useful method fo
r preparation of DNA templates toward enzymatic incorporation of unnatural
nucleosides into RNA at desired positions.