Synthesis, Conformation, and Binding Properties of Resorcarene Tetrasulfonates. Asymmetric Reorganization of Pendant Sulfonyl Groups via Intramolecular SO- - -H−O Hydrogen Bonds

Abstract

The regioselective reaction of resorcarene octaols 1 with 4 equiv of arylsulfonyl chlorides and Et 3 N in MeCN gives in 30−60% yield the C 2v symmetrical tetrasulfonates 3 . The mild electrophilic substitution (aminomethylation, bromination) of resorcarene tetrasulfonates 3 and tetraphosphates 2 takes place only in the 2-positions of unsubstituted resorcinol rings yielding distally disubstituted resorcarenes 4. The acylation of hydroxy groups in compounds 2 and 3 gives C 2v symmetrical octaesters 5 including large resorcarene tetracrown-ethers. In the minimized boat conformation of tetrasulfonates 3 the two unsubstituted resorcinol rings are vertical and the sulfonyl fragments are arranged in a C 2 symmetrical manner via intramolecular S O- - -H−O hydrogen bonds. This structure is proved by NMR and IR spectroscopy. In the case of tetrasulfonate 3c the two enantiomeric conformations interconvert in CDCl 3 with Δ G * = 11.6 kcal/mol. This is in agreement with the Δ E * value predicted by molecular mechanics in vacuo .