Oxidation of cucurbituril and its analogues

Cucurbituril is a high symmetry and rigid structure. When cucurbit[6]uril (CB[6]) was oxidized with persulfate (e.g. potassium persulfate, sodium persulfate and ammonium persulfate), the main product was perhydroxy-cucurbituril and the minor one was oxalic acid. Oxalic acid was also obtained by the oxidization of both CB[n] (n=5,7,8) and perhydrox-cucurbituril with various persulfates. As far as we know, this is the first time to discover that both cucurbit[n]uril and perhydrox-cucurbit[n]uril can be destroyed to give a small molecule-oxalic acid.