Patent ID: 7276599

Claim:
A method of manufacturing an oligonucleotide comprising a pentavalent phosphate triester, said method comprising: (a) providing a 5′ blocked-nucleoside; (b) deblocking the 5′ blocked-nucleoside to form a 5′ OH-nucleoside; (c) coupling the 5′ OH-nucleoside with a phosphoramidite of formula (IV) wherein Y is 0, S, CH 2 , CHF, CF 2 or —CH═CH—; bg is a 5′-blocking group; R′ 2 is H, OZ, a 2′-substituent, or together with R′ 4 forms a bridge; R′ 4 is H, OZ, a 2′-substituent, or together with R′ 2 forma a bridge; Z is H or a removable protecting group; Bx is a nucleobase; pg is a phosphorus protecting group; each G is 0 or S; L is an amine leaving group; G 1 is 0 or S; and q′ is 0 or 1; to form an oligonucleotide comprising a trivalent phosphite triester; and (d) oxidizing the oligonucleotide comprising a trivalent phosphite triester to form the oligonucleotide comprising a pentavalent phosphate triester; wherein at least a wash between any of the steps above is with a solvent wash comprising a toluene, pyridine, lutidine, hexane, cyclohexane, cyclohexene, a halogenated benzene, alkylated benzenes, a haloalkylbenzene, acetone, ethylacetate, methanol, ethanol, phenol, cyclic ethers, acyclic ethers, halogenated alkanes or mixtures thereof.