A direct route to chiral cyclopropylpyrimidine carbocyclicnucleoside 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
Influence of theN3-Protection Group onN1- vs.O2-Alkylation in the Mitsunobu Reaction
作者:Olaf R. Ludek、Chris Meier
DOI:10.1002/ejoc.200500801
日期:2006.2
The influence of the N3-protection group of thymine on the regioselectivity of the N1- vs. O2-alkylation under Mitsunobu conditions is described. A series of N3-protected thymine derivatives 8a–f was prepared and coupled to cyclopentanol as model compound for carbocyclic nucleoside precursors. Finally, the N3-BOM group was selected to improve our previously reported synthetic strategy to carbocyclic
pyrimidine carbocyclicnucleoside analogues bearing a quaternary center was developed via asymmetric Michael-initiated cyclopropanation. The axis chirality was observed in cyclopropyl pyrimidine carbocyclicnucleoside analogues for the first time, which was caused by the rotationally restricted NC bond in N-COPh moiety. Using (DHQD)2AQN as the organocatalyst, diverse cyclopropyl pyrimidine carbocyclic nucleoside