Distal bis(carboxymethyloxy) derivatives of thiacalix[4]arene were found to
undergo an unprecedented intramolecular cyclisation to yield lactone compo
unds 5a or 5b, the structure of lactones possessing nine-membered ring was
proved by X-ray crystallography; inherent chirality of new compounds was de
monstrated using separation on a chiral HPLC column.