<p>Disclosed is a compound represented by general formula (1) or a salt thereof, which is capable of preferentially inducing the production of IFN-? in NKT cells and is therefore useful for the prevention or treatment of cancer or infectious diseases. (In the formula, R1 represents an aldopyranose residue wherein a hydroxy group at the 6-position may be alkylated; R2 represents an optionally substituted hydrocarbon group having 1-26 carbon atoms; R3 represents a hydrogen atom or an optionally substituted hydrocarbon group having 1-26 carbon atoms; R4 represents an optionally substituted hydrocarbon group having 1-21 carbon atoms; X represents an oxygen atom or a -CH2- group; and Y represents a -CH2- group, a -CH(OH)- group or a -CH=CH- group.)</p>
