New conformationally locked bicyclic N,O-nucleoside analogues of antiviral drugs

In order to obtain rigidity within the sugar moiety of nucleosides, the bicyclic pyrimidine derivatives of N,O-isoxazolidines were designed and synthesized by using 1,3-dipolar cycloaddition of Delta(1)-pyrrolidine-1-oxide and the appropriate vinyl-nucleobases. (C) 2004 Elsevier Ltd. All rights reserved.