title: The indole side chain of tryptophan as a versatile pi-donor.
abstract: Single-armed, 15- and 18-membered lariat ether receptor systems having indolylethyl side arms bind Na+ and K+ in the ring. The indole residue serves as a pi-donor to the ring-bound cation. Whether the five- or six-membered ring interacts most directly with Na+ or K+ depends on whether the sidearm is attached to indole's 3- or 5-position. This suggests that structural as well as electronic factors are important in pi-complexation of alkali metal cations.
authors.affiliation: Division of Bioorganic Chemistry, Bioorganic Chemistry Program, and Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110, USA.
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Hu
authors.forename: Leonard J
authors.initials: LJ
authors.lastname: Barbour
authors.forename: George W
authors.initials: GW
authors.lastname: Gokel
mesh_terms: D004988:Ethers, Cyclic / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D004988:Ethers, Cyclic; D014364:Tryptophan