Carbon-13 labelling study of the coenzyme B<sub>12</sub>-dependent methylitaconate ⇌α-methyleneglutarate model rearrangement reaction and examination of potential cyclopropane intermediates
作者:Paul Dowd、Roger Hershline
DOI:10.1039/p29880000061
日期:——
alcohol (19) into the bromide (20a) was effected with phosphorus tribromide. An extensive series of experiments involving treatment of the acids and their methyl and tetrahydropyranyl esters with vitamin B12S was carried out. No methylitaconic acid (3a) could be detected in any of the reaction mixtures. However, α-methyleneglutaric acid (2a) and methylglutaconic acid (21) were observed as the reaction products
用碳13标记进行了模拟重排的模型重排,该重排模拟了依赖于辅酶B 12的酶催化的α-亚甲基戊二酸与甲氧代酸的相互转化。毫无疑问,该实验证明丙烯酸酯基团是模型中的迁移基团,就像在酶催化的重排中一样。还描述了旨在探测模型重排中可能存在的环丙基甲基中间体的实验。为此,从常见的前体环丙烷-1,1,2-三羧酸(13)开始制备顺式和反式-溴甲基环丙烷二酸(16a)和(20a)。因此,(13)被转化为酸酐(14),然后将其还原为内酯(15)。用在乙酸中的HBr打开内酯,得到所需的反式-二酸(16a)。对于顺式二酸(20a),将酸酐(14)水解,用重氮甲烷酯化,然后用三乙基硼氢化锂还原。用三溴化磷将所得的醇(19)转化为溴化物(20a)。一系列广泛的实验,涉及用维生素B 12S处理酸及其甲基和四氢吡喃基酯进行了。在任何反应混合物中均未检测到甲基衣康酸(3a)。然而,观察到α-亚甲基戊二酸(2a)和甲基戊二酸(21)作为反应产物。甲基甲苯p