This invention relates to compounds represented by the general formula [I] ##STR1## wherein, R represents an azido group, etc., R.sup.1 and R.sup.2 are the same or different and represent hydrogen atoms, etc., R.sup.3 and R.sup.4 are the same or different and represent hydrogen atoms, etc., X.sub.1 represents an oxygen atom, etc., X.sub.2 represents an oxygen atom, etc., Y represents an oxygen atom, etc., and Z represents a condensed aryl group, etc., or a pharmaceutically acceptable salt thereof, preparation processes thereof, and an agent for treating diabetes, a prophylactic agent for chronic complications of diabetes or a drug against obesity, containing, as an effective ingredient, the compound or the pharmaceutically acceptable salt thereof.