PURPOSE: To obtain a new sodium ion-selective ligand compound having high selectivity against a sodium ion, capable of being widely used in a field of an industrial process, food, a medical basic research, etc., and useful as an ion sensor (an ion electrode) having high selectivity.

CONSTITUTION: This is a compound of formula I (X and Y are each a ≥6C hydrocarbon group). For example, 2,2,3,3,8,8,9,9-octamethyl1,4,7,10,13- pentaoxacyclohexadecane. The compound of the example is obtained as follows. 2,3-Dimethyl-2,3-butanediol (A) is benzylated, subsequently the benzylated compound is allylated, and a compound (B) of formula II is obtained from the product of the allylation. On the other hand, a compound of formula III (Ts is para-toluenesulfonyl) (C) is obtained by using the compound A and benzyloxyethanol mesylate as starting materials. Finally, the compound B and the compound C are made to react with each other to obtain the objective compound.