The present invention relates to a compound represented by the following formula (1): wherein D 1 , A 1 , D 2 , R 1 , D 3 , and R 2 each have the same meaning as defined in the present specification or a salt thereof. The compound represented by the formula (1) or a salt thereof has an IKK² inhibiting activity and the like and is useful for the prevention and/or treatment of IKK²-associated diseases or symptoms and the like.