Provided are a novel compound or a salt thereof, and a pharmaceutical composition comprising the same, which selectively and strongly inhibit JAK3, exhibit an excellent activity for suppressing the growth of human peripheral blood monocytes and an excellent oral absorbability, and exhibits an activity of inhibiting IL-2-induced IFN-γ production in vivo. A compound represented by formula (I) [wherein X represents —CH═CH—, —NH—, a sulfur atom or an oxygen atom; and n represents an integer of 0 to 2], or a salt thereof.