Enantioselective Intermolecular Cyclopropanations for the Synthesis of Chiral Pyrimidine Carbocyclic Nucleosides

A direct route to chiral cyclopropylpyrimidine
carbocyclic nucleoside
analogues has been reported via highly enantioselective intermolecular
cyclopropanation reactions of N1-vinylpyrimidines with α-diazoesters.
With chiral ruthenium­(II)–phenyloxazoline complex (2 mol %)
as the catalyst, cyclopropyl pyrimidine nucleoside analogues could
be obtained in good yields (71–96% yields) with high levels
of diastereo- and enantioselectivities (10:1 to >20:1 dr and 96–99%
ee) in 1 min.