title: Macrocyclic oligoureas with xanthene and diphenyl ether units.
abstract: Two cyclic oligoureas with 64- and 80-membered rings in which two sets of three or four rigid xanthene (X) units are connected via flexible diphenyl ether (D) units were synthesized by a stepwise fragment condensation. The compounds were characterized by (1)H NMR and ESI mass spectrometry. The structure of the cyclic octamer (XXXDXXXD) was additionally confirmed by single crystal X-ray analysis. The molecule assumes a strongly folded conformation with distorted C(2)-symmetry, stabilized by intramolecular hydrogen bonds. Surprisingly, intermolecular hydrogen bonds between the macrocycles were not observed. (1)H NMR spectra suggest a C(2) symmetrical conformation of the octamer in solution also, while its kinetically stable complex with three chloride ions has no symmetry element at all.
authors.affiliation: Fachbereich Chemie, Pharmazie und Geowissenschaften, Abteilung Lehramt Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, D-55099 Mainz, Germany.
authors.forename: Denys
authors.initials: D
authors.lastname: Meshcheryakov
authors.forename: Michael
authors.initials: M
authors.lastname: Bolte
authors.forename: Volker
authors.initials: V
authors.lastname: Böhmer
mesh_terms: D018360:Crystallography, X-Ray; D047028:Macrocyclic Compounds / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D010647:Phenyl Ethers / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D014966:Xanthenes / Q000737:chemistry*
chemical_list: D047028:Macrocyclic Compounds; D010647:Phenyl Ethers; D011108:Polymers; D014966:Xanthenes; C045786:polyurea; C031538:phenyl ether