Patent ID: 6846922

Claim:
A method for the preparation of a compound of formula: wherein: R 1 is a nucleoside or an oligonucleotide; R 2 is a nucleoside linked to a solid support, or an oligonucleotide linked to a solid support; Pg is a phosphorus protecting group; comprising: providing a phosphoramidite of formula: wherein R 6 is —N(R 7 ) 2 wherein R 7 is alkyl having from one to about six carbons; or R 7 is a heterocycloalkyl or heterocycloalkenyl ring containing from 4 to 7 atoms, and having up to 3 heteroatoms selected from nitrogen, sulfur, and oxygen; and reacting said phosphoramidite with a hydroxyl group of a nucleoside linked to a solid support, or an oligonucleotide linked to a solid support; said reaction being performed in the presence of an activating reagent, said activating reagent comprising at least one pyridinium salt and at least one substituted imidazole.