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The cycloaddition reaction between C-(2-thiazolyl) nitrones and allylic alcohol takes place with complete exo selectivity when the reactions are carried out in presence of one equiv of zinc triflate. The use of a chiral dipolarophile allowed application to the methodology to the synthesis of a hitherto unknown enantiomerically pure isoxazolidinyl analogue of the C-nucleoside tiazofurin.

Research has been conducted on the enantiomerically pure 3-amino-2(5H)furanones. The synthesis of these compounds carried out via the NaH reaction with furoisoxazolidines has been carried out and the details are presented.

Investigation of the chiral auxiliaries introduction at the C- or N-atom in starting nitrones is discussed. Experiments demonstrate a stereoselective synthetic route to heterocyclic nucleoside analogues.

A novel, efficient entry to 2'-(dimethylamino)-2'-3'-dideoxynucleosides was described. The synthetic approach involves the 1,3-dipolar cycloaddition of C-alkoxycarbonyl nitrones to allyl acetate, reductive ring opening to substituted lactones, DIBALH reduction to the corresponding 3-(dimethylamino)tetrahydro-2-furanols and coupling with silylated thymine. Formal synthesis of d4T and analogous unsaturated 2',3'-dideoxynucleosides was made possible by removal of the dimethylamino group via Cope elimination.

3-Isoxazolidones can be prepared by the direct Ru[O.sub.2]/NaI[O.sub.4] oxidation of 3-unsubstituted isoxazolidines, under ethyl acetate/water biphasic conditions. This method can be used on both racemic and optically active isoxazolidines.

Two different routes which exploit the reactivity of a phosphonated nitrone are employed to obtain a new template of C-4?-truncated phosphonated nucleosides (TPCOANs) in good yields. The [beta]-anomers of TPCOANs exhibit the ablility to inhibit the reverse trancriptase of different retroviruses at concentrations in the nanomolar range, with potency comparable with that of tenofovir.