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27- and 36-membered ring peptides were prepared using glycine, (2S, 3′ S)-4-methyl-2-(2′-oxo-3′-isobutyl-1′-piperazinyl) pentanoic acid (2) and (2S,3′ S)-3-phenyl-2-(2′-oxo-3′-benzyl-1′-piperazinyl)propanoic acid as the units of peptides. The interactions of 1-phenylethylammonium (1) and p-methoxy-1-phenylethylammonium bromides (11) with these cyclic peptides were studied by 1H and 13C NMR measurements in CDCl3. It was found from these results that the peptides distinguish the enantiomers (R- and S-isomers) of the substrates. Furthermore, it was shown that the enantioface-differentiating abilities of 36-membered ring peptides are superior to those of 27-membered rings.