Isoxazole, isoxazoline and isoxazolidine analogues of C-nucleosides related to pseudouridine have been synthesized by 1,3-dipolar cycloaddition reactions of nitrile oxides and nitrones derived from mono and disubstituted uracil-5-carbaldehydes and 2,4-dimethoxypyrimidine-5-carbaldehyde. The dimethoxy derivatives have been easily deprotected to the corresponding uracils bearing the heterocyclic ring
1,3-Dipolar cycloadditions of different hydrophobic nitrones 1, 2, 3, 4 with acrylates 5 and 6 were studied in both homogenous organic solutions and aqueous suspensions. Reactions in water suspensions showed great rate accelerations over homogenous solutions. Small changes were also observed to the stereoselectivities of the reactions. Hydrophobic interactions are invoked for the observed behaviour.
Pyrrolidine analogues of C-nucleosides related to pseudouridine have been synthesized by 1,3-dipolar cycloaddition reactions of uracil-5 and 2,4-dimethoxypyrimidine-5 nitrones with allyl alcohol and methyl acrylate, and subsequent reductive cleavage of the isoxazolidine cycloadducts. The dimethoxy derivatives have been easily deprotected to the corresponding uracils bearing the pyrrolidine ring instead