A pair of artificial enantiotopic receptors la, Ib composed of (S,S) or (R,
R) chiral bicyclic guanidinium, azacrown ether and (t-butyldiphenylsilyloxy
)methyl group for amino acid zwitterions have been synthesized. The liquid-
liquid competition extraction experiments and H-1 NMR studies indicate that
the receptor la with (S,S) configuration and Ib with (R,R) configuration s
electively recognize L- and D-aromatic amino acids, respectively. (C) 1999
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