COMPUTATIONAL STUDIES OF CALIX[4]ARENE HOMOLOGS - INFLUENCE OF 5,11,17,23-SUBSTITUENTS AND 25,26,27,28-SUBSTITUENTS ON THE RELATIVE STABILITY OF 4 CONFORMERS
T. Harada et al., COMPUTATIONAL STUDIES OF CALIX[4]ARENE HOMOLOGS - INFLUENCE OF 5,11,17,23-SUBSTITUENTS AND 25,26,27,28-SUBSTITUENTS ON THE RELATIVE STABILITY OF 4 CONFORMERS, Tetrahedron, 49(27), 1993, pp. 5941-5954
The effects of 5,11,17,23- and 25,26,27,28-substitutents on the relati
ve stability of four conformers of calix[4]arene are discussed on the
basis of a computational method using molecular mechanics (MM3) calcul
ations. It is shown that a substituent in the lower rim site has a dec
isive role in the determination of the stability order among four conf
ormers of calix[4]arene, while a substituent in the upper rim site onl
y slightly affects the energy differences. It is also shown that in [1
(4)]metacyclophanes with no substituent in the lower rim the structure
of 1,2-alternate conformers is very different from the typical 1,2-al
ternate structure common to calix[4]arenes.