A macrocyclic receptor based on a bischromenylurea and an
,
'-(
o,o'-dialkyl)diphenyl-
p-xylylenediamine spacer provides a
C2 chiral cavityto associate carboxylates by H-bonds. The extent of the selectivity obtained for the racemic receptor
2 and enantiomerically pure (
S)-naproxenis 7.2:1. Steric repulsions close to the cavity are decisive for the chiral selectivity.