Template Synthesis, Structure, and Binding Properties of Macrocyclic S, O -Lactones

The synthesis, structures, and binding properties of mixed S, O-lactones, a new family of macrocyclic carbonyl compounds, are described. The synthesis involves the use of cyclic stannoxathiane (1) as a templated mercapto alcohol, which reacts with diacyl dihalides to provide monomeric 2, dimeric 3, trimeric 4, and tetrameric 5 macrocyclic products in good overall yields and high stereospecificity. The dimeric derivatives 3 bind silver nitrate via their thiolactone groups when n is even but do not bind when n is odd. These regularities follow the conformational regularities of these compounds and demonstrate the relationship between conformation and binding. In addition, evidence is provided (crystal structures) that the conformation of the ligating molecule is preserved upon binding. The implications of these findings for the use of carbonyl groups in adjusting the conformation and binding properties of macrocyclic compounds are indicated.