Cycloaddition reactions with both of uridine and 2-thiouridine derivatives

The present paper described work directed towards reactions of both of 2',3',5'-tri-O-acetyl uridine and its 2-thioanlogue with either of 2H- pyran-2-one, 4,6-dimethyl-2H-pyran-2-one and 2,3-bis [dibromomethyl] benzene to afford cycloaddition products