New water‐soluble calixarenes modified with amino acids at the upper rim

Calix[n]arenes (n = 4 and 6) modified with L‐cysteines were synthesized. These calix[n]arenes were water‐soluble, particularly, at acidic and basic pH regions. The critical micelle concentrations (estimated by surface tension) appeared at (0.50‐3.2) · 10−5 M. The “hydrophobicity” of these cavities was estimated by fluorescence of 8‐anilino‐1‐naphthalene‐sulfonate (ANS): it showed that these calix[n]arenes become most hydrophobic at pH 5‐6. The selectivity in guest inclusion was significantly affected by the medium pH.