Regio- and Enantioselective Synthesis of Chiral Pyrimidine Acyclic Nucleosides via Rhodium-Catalyzed Asymmetric Allylation of Pyrimidines

A direct route to
branched N-allylpyrimidine analogues
is herein reported via the highly regio- and enantioselective asymmetric
allylation of pyrimidines with racemic allylic carbonates. With [Rh­(COD)­Cl]2/chiral diphosphine as the catalyst, a range of chiral pyrimidine
acyclic nucleosides could be obtained under neutral conditions in
good yields (up to 95% yield) with high levels of regio- and enantioselectivities
(15:1 to >40:1 B/L and up to 99% ee). Furthermore, chiral pyrimidine
acyclic nucleoside bearing two adjacent chiral centers has been successfully
synthesized by asymmetric dihydroxylation.