A new synthetic method for the N-alkyloxycarbonylation of adenine and guani
ne nucleosides was developed and used for the preparation of RNA-phosphoram
idites carrying photolabile sugar and nucleobase protecting groups. From th
ese building blocks, a heptameric oligoribonucleotide was prepared by autom
ated synthesis, followed by detachment from the solid support and photolyti
c deprotection under mild conditions. The presented strategy allows a simpl
e preparation of 3'-O-aminoacylated RNA-sequences.