Reactions of N-(o-carboxybenzoyl)-L-leucine: intramolecular catalysis of amide hydrolysis and imide formation by two carboxy groups
作者:Alvaro B. Onofrio、José C. Gesser、Antonio C. Joussef、Faruk Nome
DOI:10.1039/b007047p
日期:——
The intramolecular reactions of N-(o-carboxybenzoyl)-L-leucine (1) were studied in aqueous solution, as a function of the hydrogen ion concentration. Two competing reactions were observed: i) cyclization to form the imide N-phthaloylleucine, and ii) hydrolysis of (1) to phthalic acid and leucine. Individual rate constants for cyclization and hydrolysis were obtained from the overall rate constants and product distributions. Imide formation predominates under highly acidic conditions (H0 < −1) and hydrolysis in the H0 > −1 to pH 5 range. In the hydrolysis reaction, the neighbouring carboxy group participates nucleophilically and in the pH 3–5 range there is a requirement for participation of the second carboxy group as a general acid. Imide formation also requires participation
of two carboxy groups in the pH 2–5 range, and shows a bell-shaped pH–rate constant profile. Possible mechanisms for these reactions are discussed.
研究了 N-(邻羧基苯甲酰基)-L-亮氨酸 (1) 在水溶液中的分子内反应,该反应随氢离子浓度变化。观察到两个竞争反应:i)环化形成酰亚胺N-邻苯二甲酰亮氨酸,和ii)(1)水解成邻苯二甲酸和亮氨酸。环化和水解的各个速率常数是从总速率常数和产物分布中获得的。在高酸性条件 (H0 < -1) 下主要形成酰亚胺,在 H0 > -1 至 pH 5 范围内则主要发生水解。在水解反应中,邻近的羧基以亲核方式参与,并且在pH 3-5范围内,需要第二个羧基作为一般酸参与。酰亚胺的形成也需要参与
两个羧基在 pH 2-5 范围内,并显示出钟形 pH 速率常数曲线。讨论了这些反应的可能机制。