Synthesis and photostability of methoxycinnamic acid modified cyclodextrins

Various cyclodextrins, alpha, beta and gamma, were esterified with 4-methoxy-, 2,4,5- and 2,4,6-trimethoxycinnamic acids. Upon esterification with β-cyclodextrin, the photostability of 2,4,5-trimethoxycinnamate increased while no improvement was observed for 4-methoxycinnamate and 2,4,6-trimethoxycinnamate. However, increase in the photostability of 4-methoxycinnamoyl moiety could be observed when esterified with α-CD and that of 2,4,6-trimethoxycinnamoyl moiety could be observed after being esterified with γ-CD. These photostability data together with the 2D NMR analyses indicated that the 4-methoxycinnamoyl, 2,4,5-trimethoxycinnamoyl and 2,4,6-trimethoxy cinnamoyl moieties could enter the α-CD, the β-CD, and the γ-CD cavities, respectively.