Disclosed is a medical agent which is excellent in stability in living bodies andwater solubility, while having excellent PI3K inhibitory activity. The medicalagent is thus useful for prevention or treatment of cancers. Specifically disclosedis a compound represented by the formula (I) below or a pharmaceutically acceptablesalt thereof. (I) (In the formula, X represents a single bond orthe like； Y represents a single bond or the like (provided that X and Y are not singlebonds at the same time)； Z represents a hydrogen atom or the like； m represents aninteger of 1 or 2； and R
