The transformation of nor-seco-cucurbit[10]uril to cucurbit[5]uril and cucurbit[8]uril controlled by its own concentration

Nor-seco-cucurbit[10]uril (ns-CB[10]) is a kinetic product with unique structure. The single bridged methylene in its structure makes the molecular cavity of ns-CB[10] more deformable when compared to ordinary cucurbit[n]uril, reducing its structural stability. Repeated experiments showed that ns-CB[10] gradually cracks in an acidic solution and changes the specificity of cucurbit[5]uril (CB[5]) and cucurbit[8]uril (CB[8]) under more robust acidic solutions and when heated. A series of experiments were designed to study the transformation behavior of ns-CB[10]. It was found that the concentration of ns-CB[10] was correlated with the content distribution of CB[5] and CB[8]. This study explores the influencing factors and mechanisms of the transformation of ns-CB[10] to CB[5] and CB[8]. The results are of great significance for the application of ns-CB[10], understanding the formation mechanism of cucurbit[n]urils. Furthermore, it provides a new pathway for synthesizing new cucurbit[n]urils. (c) 2024 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.