Synthesis of modified oligonucleotides containing 4-guanidino-2-pyrimidinone nucleobases

Oligonucleotides incorporating 4-guanidino-2-pyrimidinone nucleobases have been prepared. These nucleobase analogues were designed to mimic the double hydrogen bond donor pattern of protonated cytosines in parallel triple helices. Guanidine-, N-methyl-, N,N-dimethyl-, and N,N′-dimethylguanidine-containing nucleoside H-phosphonates were used for the synthesis of oligonucleotide analogues with minor modifications in standard solid-phase procedures.