Compounds of a formula (I) and their pharmaceutically-acceptable salts are disclosed. The compounds have glucokinase-activating effect and are therefore useful for treatment of diabetes and obesity.R1 and R2 each independently represent a lower alkyl group； X1 represent a group of a formula (II-1):wherein:R11 and R12 each independently represent a hydrogen atom or a lower alkyl group, or taken together with the nitrogen atom to which they bond, R11 and R12 may form a 4- to 7-membered nitrogen-containing aliphatic ring (one carbon atom constituting the 4- to 7-membered nitrogen-containing aliphatic ring may be replaced by an oxygen atom), or taken together with a carbon atom in (CH2)m, R11 and R12 may form a 4- to 7-membered nitrogen-containing aliphatic ring； m indicates an integer of from 1 to 3.
