A therapeutic agent for diabetes, which comprises a compound of the formula [I]
wherein
Xis a group of the formula
wherein R4 and R5 are the same or different and each is a hydrogen atom, an optionally substituted alkyl having 1 to 5 carbon atoms and the like, and R6 is a hydrogen atom or an amino-protecting group; R1 is an optionally substituted alkyl having 1 to 5 carbon atoms, an optionally substituted alkenyl having 2 to 6 carbon atoms and the like, R2 is a hydrogen atom, an optionally substituted alkyl having 1 to 5 carbon atoms and the like, R2' is a hydrogen atom, and R3 is an optionally substituted alkyl having 1 to 5 carbon atoms and the like, a prodrug thereof, a pharmaceutically acceptable salt thereof, a hydrate thereof and a solvate thereof.
The compound of the present invention shows superior blood sugar decreasing action on the state of hyperglycemia, but does not affect the blood sugar when it is in the normal range or in the hypoglycemic state, which means that it is free of serious side effects such as hypoglycemia. Therefore, the compound of the present invention is useful as a therapeutic drug for diabetes and also useful as a preventive of the chronic complications of diabetes.