Photocycloadditions of 2', 3', 5'-triacetyluridine to tetramethylethylene, isopropenyl acetate, 1, 1-diethoxyethylene, and vinylene carbonate are described. The rearrangement of the vinylene carbonate adduct to 2', 3', 5'-triacetyl-5-formylmethyluridine followed by oxidation to the 5-carboxymethyl or decarbonylation to the 5-methyl (ribothymidine) derivative is also described.
![(3aξ,3bξ)-4-(tri-O-acetyl-β-D-ribofuranosyl)-(3ar,3br',7ac',7bc)-tetrahydro-[1,3]dioxolo[4',5':3,4]cyclobuta[1,2-d]pyrimidine-2,5,7-trione结构式](https://image.chemsrc.com/caspic/034/60543-63-7.png)