toxicity (ip LD50's = 15-50 mg/kg) is restored in oxabicyclohepta-2(3),5(6)-dienes substituted in the 2- and 3-positions with bis(methyl carboxylate), bis(ethyl carboxylate), and diethyl phosphonate/ethyl carboxylate, whereas the dicarboxylic acid, bis(tert-butyl carboxylate), and bis(dimethyl phosphonate) are inactive. The diene adducts do not inhibit the cantharidin binding site of PP2A. Two observations
不连续的结构-活性关系表明了作用方式的改变,并导致发现了可能的新型代谢激活机制。内皮
除草剂(exo,exo-7-oxabicyclo [2.2.1]
庚烷-2,3-二
羧酸)对小鼠的毒性(ip LD50 = 14 mg / kg)归因于蛋白
磷酸酶2A(PP2A)的抑制作用)在cantharidin结合位点。通过引入2,3-或5,6-双键降低了效力。出人意料的是,高毒度(ip LD50 = 15-50 mg / kg)被还原为在oxabicyclohepta-2(3),5(6)-二烯在2和3位被双(
羧酸甲酯),双(乙基)取代
羧酸盐)和
二乙基膦酸酯/
羧酸乙酯,而二
羧酸,双(
羧酸叔丁酯)和双(
膦酸二甲酯)则没有活性。二烯加合物不抑制PP2A的
邻苯二酚结合位点。有两个观察结果提供了另一个可行的假设,即活性而不是非活性二烯加合物是前毒素:GC分析表明,选定的双环二烯容易通过逆Diels-Alder反应发