A complex formed by two 1,6-anhydro-beta-maltoses with peroxide and two sodium ions has been isolated and determined to be [Na-2(1,6-anhydro-beta-maltose)(2)(H2O)(3)]O-2 by X-ray crystallography. The O-2 moiety, 1.496(2)angstrom for the O-O distances in the complex was identified as a discrete peroxide dianion, whereas two sodium and two carbohydrate molecules constitute a binuclear complex counter cation. The complex containing the discrete peroxide dianion was proven to be a useful oxidizing agent, which Successfully oxidized alpha,beta-unsaturated ketone to epoxyketone.