A process for removal of exocyclic nucleobase nitrogen-protecting groups
from a protected oligonucleotide comprising at least one 2'-O-protected
nucleotide or 2'-halo-, such as a 2'-fluoro-, nucleotide is provided. The
process comprises contacting the protected oligonucleotide with a
solution of an inorganic base selected from the group consisting of
lithium hydroxide, lithium carbonate, sodium carbonate and potassium
carbonate.