MODIFIED DIDEOXYNUCLEOSIDES : SYNTHESIS OF 2'-N-ALKYL-3'-HYDROXYALKYL-1',2'-ISOXAZOLIDINYL THYMIDINE AND 5-FLUOROURIDINE DERIVATIVES

Abstract Isoxazolidine nucleosides bearing an hydroxyl group at C 3 , have been prepared in only three steps, with overall high yields. The synthetic approach is based on the 1,3-dipolar cycloaddition of 3-carboxyalkyl- or acylnitrones to vinyl acetate, followed by condensation with silylated thymine or 5-fluorouracil and NaBH 4 reduction.