New methods to obtain 1,2-bridged calix[4]arene-biscrowns in the 1,2-a
lternate conformation are described. The stereochemistry of the proxim
al double functionalization reaction is mainly governed by the solvent
, the length of the polyether units and the base used to deprotonate t
he calix[4]arene. (C) 1997 Elsevier Science Ltd.