Dual recognition of a C–G pyrimidine–purine inversion site: synthesis and binding properties of triplex forming oligonucleotides containing 2′-aminoethoxy-5-methyl-1H-pyrimidin-2-one ribonucleosides

The synthesis of a new ribonucleoside analogue, which combines two modifications, namely a 2′-aminoethoxy side-chain on the ribose and a 5-methyl-1H-pyrimidin-2-one (4HT) unit as a base replacement, is presented. This building block was incorporated into triplex forming oligonucleotides and the binding properties to CG inversion sites in DNA duplex targets were studied. The data clearly show that the 4HT base selectively recognizes the CG base-pair, while the aminoethoxy chain adds to the overall stability of the triple helix.