Binding constants (Ka) of calix[4]arene 1, 3-alternate conformer 2 bearing two ester groups for alkali picrates have been determined in tetrahydrofuran. It has been established that (i) 2 forms the 1:1 complexes with alkali metal cations, (ii) the M+-2 complexes are not considerably solvent-separated because of the “weak encapsulation effect” for two ester groups of 2, however the Ka values for 2 are generally as large as those for 1 having four ester groups. Interestingly, the largest Ka was attained for K+ and 2 complexes. This is the first comparison for the recognition capacity between two ester groups and four ester groups in calix[4]arene ester complexes. © 2003, Japan Oil Chemists' Society. All rights reserved.