PARALLEL DNA CONTAINING PYRAZOLO[3,4-D]PYRIMIDINE ANALOGUES OF ISOGUANINE

The phosphoramidites of 8-aza-7-deaza-2′-deoxyisoguanosine (1a) and its bromo derivative 1b as well as of 6-aza-2′-deoxyisocytidine and its 5-methyl derivative (3a,b) were synthesized. Parallel-stranded duplexes containing the nucleosides 1a,b show a significantly enhanced duplex stability compared to those containing 2′-deoxyisoguanosine.