SYNTHESIS OF 2'-DEOXYNUCLEOSIDE 5'-METHYLENEBIS-(PHOSPHONATE)S USING 2-(4-NITROPHENYL)ETHYL METHYLENE-BIS(PHOSPHONATE) AS THE PHOSPHONYLATING AGENT

2-(4-Nitrophenylethyl) methylenebis(phosphonate) (1) has been prepared by reaction of 2-(4-nitrophenyl)ethyl alcohol with methylenebis(phosp honyl) tetrachloride. Compound 1 was treated with diisopropylcarbodiim ide (DIC) to give bicyclic intermediate 2, which in reaction with suit ably protected 2'-deoxynucleosides 3 gave P-1,P-2-disubstituted methyl enebis(phosphonate)s 4. Removal of the nitrophenylethyl group by beta- elimination with DBU afforded the corresponding 2'-deoxynucleoside 5'- methylene-bis(phosphonate) analogues 5.