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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Macrocyclic oligoureas with xanthene and diphenyl ether units
Denys Meshcheryakov1, Michael Bolte, Volker Böhmer
1Fachbereich Chemie, Pharmazie und Geowissenschaften, Abteilung Lehramt Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, D-55099 Mainz, Germany.
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.
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