Reactivity of imidazolidin-4-one derivatives of primaquine: implications for prodrug design
作者:Paula Chambel、Rita Capela、Francisca Lopes、Jim Iley、José Morais、Luís Gouveia、José R.B. Gomes、Paula Gomes、Rui Moreira
DOI:10.1016/j.tet.2006.08.026
日期:2006.10
imidazolidin-4-one. The kinetically determined pKa values are ca. 3.6–4.0, i.e., 4 pKa units lower than those of amino acid amides, thus implying that hydrolysis of imidazolidin-4-ones at pH 7.4 involves the unionized form. Reactivity of this form decreases with the steric crowding of the amino acid α-substituent. In contrast, the rate constant for the spontaneous decomposition of the unionized form increases
与基于肽的咪唑啉丁-4-酮相比,由抗疟疾药物的N-(α-氨基酰基)衍生物,伯氨喹和酮合成的那些在37°C的pH 7.4中出乎意料地稳定。在60°C的pH范围0.3–13.5下,研究了基于伯氨喹的咪唑啉丁-4-酮的水解动力学。水解成母体α-氨基酰基伯氨喹的特征是S形的pH速率分布,反映了咪唑烷二-4-酮的结合形式和质子化形式(在N-1下)的自发分解。动力学确定的p K a值为ca。3.6–4.0,即4 p K a单元比氨基酸酰胺的单元低,因此暗示在pH 7.4的咪唑烷基-4-酮的水解涉及联合形式。该形式的反应性随氨基酸α-取代基的空间拥挤而降低。与此相反,速率常数的非离子化形式急剧增加用于从环酮衍生的咪唑烷-4-酮,可由解释的观察自发分解余应变(内应变)的影响。这些结果与水解的涉及一个S的机制一致Ñ酰胺基离去后,咪唑啉丁-4-一C2-N3键的1型单分子裂解。在计算研究的支持下,质子化咪唑啉丁