Condensation of thymine with diacetyl-D-xylal and triacetyl-D-glucal afforded the unsaturated nucleosides 1, 6 and 7. After deacetylation and selective protection of the primary hydroxy groups in the case of the glucose derivatives, these compounds were either submitted to Mitsunobu reaction with hydrazoic acid to give the azides 4, 14 and 15, or oxidised with PDC–molecular sieves to give the unsaturated keto