Ether and amide derivatives are disclosed, which are represented by the following formula (I) and its pharmaceutical acceptable salt, and which are useful for the treatment of diabetes. R1—A—R2  (I) wherein (with the provisos that (i) when A is —O—, then n is 2 or 3 (ii) when then n is 1 or 2. R3 is OH—, CH3SO2NH—, CF3SO2NH—, CH3SO2NHCH2—, CF3SO2NHCH2—, HOOC—, CH3OOC—, HOOC—CH2SO2NH—, CF3—CH2SO2NH—,  R8—NHSO2—, R8—NHSO2—CH2—, HOOC—CH2—O—, HSO3N═CH—, or R9—SO2NHCO—; R4 is H, OH, O-alkyl or O—CH2OCH3; R5 is H, halogen atom, —CH2COOH or OH; R6 and R7 are hydrogen, t-butyl or pyrolidyl; R8 is hydrogen or lower alkyl; R9 is alkyl or thienyl; R10 is lower alkyl) or a pharmaceutically acceptable salt.