Modified nucleosides from nitrones: a new and efficient stereoselective approach to isoxazolidinyl thymidine derivatives

The addition of the sodium enolate of methyl acetate to the N-benzyl nitrone 4 derived from D-glyceraldehyde affords the 3-substituted isoxazolidin-5-one 6a with a high degree of syn selectivity and in quantitative chemical yield; its further elaboration leads to the preparation of the important isoxazolidine nucleoside analogue 2a in enantiomerically pure form.