Borane-amine complexes--versatile reagents in the chemistry of nucleic acids and their analogs

A new method for synthesis of N-alkylated nucleosides was developed. Exceptionally mild and selective conversion of N-acyl to the corresponding N-alkyl nucleosides was achieved by reduction with borane-amine complexes. The borane-amine complexes were also used as efficient scavengers of a 4,4'-dimethoxytrityl (DMT) cation. Neutralization of the cation eliminated the boranophosphate group degradation during acidic DMT deprotection and allowed milder acidic conditions for the deprotection.