Unusual cone conformation retention in calix[4]arenes

Use of a regioselective O-alkylation, C-dealkylation synthetic sequence gen erates an 'ABAB' calix[4]arene, 4, which contains only two upper rim t-buty l groups and yet retains the cone conformation. Further substitutions can t hen be carried out independently on the upper and/or lower rims of the A an d/or B subunits, with retention of conformation. Complexation studies show that 4 retains its cone conformation in the presence of alkali metals from sodium to cesium. Thus 4 remains in the cone conformation in solid state, i n solution and on complexation. (C) 2001 Elsevier Science Ltd. All rights r eserved.