THE PRESENT INVENTION PROVIDES A COMPOUND REPRESENTED BY THE FORMULA (I): WHEREIN EACH SYMBOL IS AS DEFINED IN THE DESCRIPTION, OR A SALT THEREOF. THE COMPOUND OR A SALT THEREOF OR A PRODRUG THEREOF HAS A GPR40 RECEPTOR FUNCTION MODULATING ACTION AND IS USEFUL AS AN INSULIN SECRETAGOGUE OR AN AGENT FOR THE PROPHYLAXIS OR TREATMENT OF DIABETES AND THE LIKE.