Synthesis of Chiral Acyclic Nucleosides by Sharpless Asymmetric Dihydroxylation: Access to Cidofovir and Buciclovir

An
efficient method to construct chiral acyclic nucleosides via
Sharpless asymmetric dihydroxylation of N-allylpyrimidines
or N-alkenylpurines is reported. A range of chiral
acyclic nucleosides with two adjacent hydroxyl groups present on the
side chains could be produced in good yields (up to 97% yield) and
excellent enantioselectivities (90–99% ee). The synthetic utility
of the reaction was demonstrated by the catalytic asymmetric synthesis
of (S)-Cidofovir and (R)-Buciclovir.