Pressocucurbit[5]urils: synthesis and supramolecular properties

                                 Lukáš Ustrnul, Vladimír Šindelář


Cucurbit[n]urils (CB[n]) are macrocyclic compounds known for ability to bind organic and inorganic
guests in water with high affinity.^1 The smallest derivative of this family of compounds - CB[5]
consist of five glycoluril monomer units and it is able to include only small solvent molecules and
gases in its cavity.^2 CB[n] chemistry was explored almost exclusively in water and acidic media
due to limited solubility in organic solvents.

Synthesis and properties of novel macrocycles constructed from propanediurea (Me[10]prCB[5])^3,4
and glycoluril (GU[1]-Me[8]prCB[5])^5 unit will be presented. In comparison to other cucurbiturils
this compound differs in a shorter carbonyl portals distance and has better solubility in water and
organic solvents.

GU[1]-Me[8]prCB[5] is well soluble in methanol. It allowed us to look deeply into supramolecular
chemistry of CB[n]s in this organic polar solvent. We described exceptionally strong binding of
cations which is even higher than interaction between potassium and crown ethers. The same
pressoCB[5] derivative exhibits cation-modulated self-assembly into tetrameric aggregate. The
tetramer is stabilized by the addition of up to one equivalent of a cation but is fully
disassembled in the presence of 2 equivalents of the cation. Cations can thus be used to tune the
aggregation of macrocycle in solution.

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(1) J. Lagona, P. Mukhopadhyay, S. Chakrabati, L. Isaacs, Angew. Chem. Int. Ed. 2005, 44, 4844

(2) Y. Miyahara, K. Abe, T. Inazu, Angew. Chem. Int. Ed. 2002, 41, 3020-3023

(3) X. Jiang, X. Yao, X. Huang, Q. Wang, H. Tian, Chem. Commun. 2015, 51, 2890

(4) L. Ustrnul, P. Kulhanek, T. Lizal, V. Sindelar, Org. Lett. 2015, 17, 1022

(5) L. Ustrnul, M. Babiak, P. Kulhanek, V. Sindelar, in process of publication