Mixed backbone oligonucleotides (MBOs) (containing ionic and nonionic
internucleotidic linkages) in which the non-ionic segments are either
methylphosphotriester (PO-OMe) or primary phosphoramidate (PO-NH2) lin
kages have been prepared using the recently described N-pent-4-enoyl (
PNT) nucleoside phosphoramidates and H-phosphonates. Biophysical prope
rties and stability studies suggest that these MBOs are novel antisens
e molecules.