Reversible ring-opening reactions of triazolobenzo- and triazolothienodiazepines in acidic media at around body temperature.
作者:NOBUO INOTSUME、MASAHIRO NAKANO
DOI:10.1248/cpb.28.2536
日期:——
Hydrolytic reactions of triazolobenzo- and triazolothienodiazepines (estazolam and etizolam) as well as a thienodiazepine (clotiazepam) were studied spectrophotometrically. Cleavage reactions of the azomethine bonds of estazolam and etizolam were reversible and the open-ring compounds were in equilibrium with the closed-ring compounds (protonated forms of the parent drugs). However, little spectral change was observed in clotiazepam. The rate of ring-closure reaction was greater than that of ring-opening reaction in estazolam whereas the opposite was the case in etizolam. The activation energies of the forward and reverse reactions were obtained from Arrhenius-type plots. In addition, the pKa value of etizolam was determined.
三唑苯并二氮杂硫和三唑噻吩二氮杂苯(埃司唑仿和依他唑仿)以及一个噻吩二氮杂苯(氯噻唑仿)的水解反应通过光谱法进行了研究。埃司唑仿和依他唑仿的亚甲基键断裂反应是可逆的,开环化合物与闭环化合物(原药的质子化形式)之间处于平衡。然而,在氯噻唑仿中观察到的光谱变化很小。埃司唑仿的闭环反应速率高于开环反应,而依他唑仿则相反。通过阿伦尼乌斯类型的图谱获得了正反应的活化能。此外,测定了依他唑仿的pKa值。