Modified dideoxynucleosides: Synthesis of 2′-N-alkyl-3′-hydroxyalkyl-1′,2′-isoxazolidinyl thymidine and 5-fluorouridine derivatives

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 NaBH4 reduction. (C) 1996 Elsevier Science Ltd