Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. Engl. 2/1989)
The cover picture shows a trefoil knot, the topology of which has been realized for the first time in a “low molecular weight” compound. An 86-membered macroheterocycle containing 14 oxygen and 8 nitrogen atoms---with a molecular weight of 1690!---has this structure in solution, as shown by NMR studies. Whereas the isomeric, unraveled macrocycle exhibits a well-resolved, relatively easily interpretable 1H NMR spectrum, the molecular trefoil knot gives a spectrum displaying broad, poorly resolved signals in the arene region. Compounds with knot topologies are of considerable theoretical interest and have long intrigued chemists. Details on the synthesis and properties of these new molecular trefoil knots are reported by C. 0. Dietrich-Buchecker and J.-P. Sauvage on p. 189 ff.