This study confirms the hypothesis that bambusurils (BUs) with equatorial sulfur atoms cannot assume an anion-binding jigger conformation due to strong intramolecular van der Waals attractive interactions. NMR, X-ray crystallography, and computation with newly synthesized eq-semithio-BU and ax-semiaza-eq-semithio-BUs indicate that they all assume compact conformations. Intramolecular distances and a torsional angle serve as reliable indicators of the conformation of any BU. Chemoselective alkylation at the peripheral (equatorial) thiourea functions provides a convenient entry to novel hetero-BUs.
Bibliographical noteFunding Information:
The authors are grateful for financial support from Israel Ministry of Science Technology and Space (MOST) Grant 3-10855 and the Open University of Israel (OUI). The authors thank Dr. Natalia Fridman from the crystallographic lab at the Schulich Faculty of Chemistry, Technion, for her valuable contribution to the X-ray crystallographic efforts.
© 2019 American Chemical Society.