Problems of the present invention is to provide a novel compound or a salt thereof capable of activating natural killer T cell, a natural killer T cell activating agent containing such a compound or a salt thereof, and a pharmaceutical composition. The compound of the present invention is a compound represented by the following formula (1) or a salt thereof. It is preferable that total carbon number of the number of carbon atoms in the monovalent hydrocarbon group in R 1 in the formula (1) excluding a sustitutent and the number of carbon atoms in the divalent hydrocarbon group in X 1 is 5 to 50. The natural killer T cell activating agent contains the aforementioned compound or a salt thereof. The pharmaceutical composition contains the aforementioned compound or a pharmacologically acceptable salt threof.
