Kinetics and Mechanism of the Addition of Nucleophiles to α,β-Unsaturated Thiol Esters
作者:Rosemarie F. Hartman、Seth D. Rose
DOI:10.1021/jo060191+
日期:2006.8.1
δ-unsaturated thiol ester (crotonyl or sorboyl) have been prepared. These compounds are subject to nucleophilic attack at the CC conjugated to the thiol ester carbonyl group. The kinetics of the reactions of these thiol esters with N-acetyl-l-cysteine (NAC), N-acetylcysteamine, and N2-acetyl-l-lysine (NAL) have been studied, and the thiol addition products have been identified. The reaction rates increased
已经制备了含有对紫外线的生色团的对甲氧基肉桂酸酯,对甲氧基肉桂酰胺或邻氨基苯甲酸酯和α,β-或α,β,γ,δ-不饱和硫醇酯(巴豆酰基或山梨酰基)的化合物。这些化合物在与硫羟酸酯羰基共轭的CC上遭受亲核攻击。这些硫醇酯与N-乙酰基-1-半胱氨酸(NAC),N-乙酰基半胱胺和N 2-乙酰基-l反应的动力学-赖氨酸(NAL)已进行了研究,并确定了巯基加成产物。在较高的pH值下,反应速率增加,并且NAC硫醇盐与巴豆酰基硫醇酯在1:1(v / v)乙腈/ HEPES水溶液中的反应由于烯醇盐中间体的质子化而显示出缓冲液催化作用。在相同浓度下,NAC与巴豆酰硫醇酯在pH值为9.8时的反应比NAL约多300倍。另外,发现巴豆酰基硫羟酸酯对NAC添加的反应性比山梨糖基硫羟酸酯的反应性高7.9倍。这些不饱和硫醇酯可作为将UVA和UVB防晒霜与皮肤外层共价结合的手段,以提供持久的保护。