Antamanide was prepared by the 9-fluorenylmethyloxycarbonyl (Fmoc)-based solid-phase method, and the transport of L-Phe-OMe and L-Leu-OMe through an organic liquid membrane mediated by the synthetic antamanide was examined. It was found that antamanide has an ability to transport L-Phe-OMe·HCl twice as efficiently as L-Leu-OMe·HCl. Affinity between the phenyl groups present in both the host and guest may be responsible for the difference.