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, R.sup.1 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).