AN OBJECTIVE OF THE PRESENT INVENTION IS TO PROVIDE WATER-SOLUBLE PRODRUGS THAT CAN BE ADMINISTERED PARENTERALLY, AND WHICH SHOW EXCELLENT WATER SOLUBILITY AND SMALL INTERSPECIES OR INDIVIDUAL DIFFERENCES AND ARE RAPIDLY CONVERTED TO THE ACTIVE FORM BY CHEMICAL CONVERSION. THIS INVENTION PROVIDES WATER-SOLUBLE PRODRUGS REPRESENTED BY FORMULA (1), OR PHARMACEUTICALLY ACCEPTABLE SALTS, OR HYDRATES OR SOLVATES THEREOF, (WHEREIN, R¹ REPRESENTS A HYDROGEN ATOM, OR C1-C6 ALKYL GROUP； W REPRESENTS A DIVALENT GROUP COMPRISING A TERTIARY AMINO GROUP OR SULFONYL GROUP； AND Y REPRESENTS A RESIDUE OF A COMPOUND REPRESENTED BY Y-OH COMPRISING AN ALCOHOLIC HYDROXYL GROUP).
