Download PDF Opens in a new window. Article suggestions will be shown in a dialog on return to ScienceDirect. ... Please enable JavaScript to use all the features on this page. ... 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 Δ 1 -pyrrolidine-1-oxide and the appropriate vinyl-nucleobases. ... The bicyclic pyrimidine ...