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.