Nucleosidyl-O-Methylphosphonates: a pool of monomers for modified oligonucleotides.

An unique set of 5'-O- and 3'-O-phosphonomethyl derivatives of four natural 2'-deoxyribonucleosides, 1-(2-deoxy-beta-D-threo-pentofuranosyl)thymine, 5'-O- and 2'-O-phosphonomethyl derivatives of 1-(3-deoxy-beta-D-erythro-pentofuranosyl)thymine, and 1-(3-deoxy-beta-D-threo-pentofuranosyl)thymine, has been synthesized as a pool of monomers for the synthesis of modified oligonucleotides. The phosphonate moiety was protected with 4-methoxy-1-oxido-2-pyridylmethyl ester group, serving also as an intramolecular catalyst in the coupling step.