Syntheses and properties of oligodeoxyribonucleotide analogues having diastereochemically pure phosphoramidate linkages.

The oligothymidilate analogues, having stereoregular and alternative phosphormorpholidate/phosphodiester backbone, were synthesized from the diastereochemically pure dimer blocks by phosphorbisamidite method. The phosphormorpholidate linkage of the oligothymidilate analogues were resistant to snake venom phosphodiesterase, and no cleavage of the phosphodiester linkage of the analogues were slowly cleaved by the nuclease was slow. The abilities of isomers to form the complexes with poly(dA) greatly depended on their structures.