A novel way of preparing 11C labelled methyl esters using [11C]methanol and either BF3 etherate or trimethylsilyl chloride as catalyst was investigated. Radiochemical yields with BF3 etherate were between 30 and 33% for [11C]methyl benzoate and less than 1% for [11C]methyl thio salicylate. No [11C]methyl ester formation could be observed with trimethylsilyl chloride for all compounds investigated. This method is an alternative to using [11C]methyl iodide in the presence of a base. It is particularly suited for carboxylic acids bearing functional groups which would compete for [11C]methyl iodide, thus eliminating the need to introduce protecting groups. However, o-anisic acid formed [11C]methyl salicylate in 33–30% decay corrected radiochemical yield due to hydrolytic cleavage of the methyl ether, and none of the desired [11C]methyl 2-methoxy benzoate could be obtained. When salicylic acid was used as starting material, [11C]methyl salicylate could only be obtained in 5–8% decay corrected radiochemical yield. Copyright © 2004 John Wiley & Sons, Ltd.
研究了一种新颖的制备11C标记甲酯的方法:使用[11C]
甲醇和
BF3乙醚络合物或三
甲基氯硅烷作为催化剂。使用
乙醚络合物时,[11C]甲基
苯甲酸酯的放射
化学产率为30-33%,而[11C]甲基
硫代水杨酸酯的产率低于1%。对于所有研究过的化合物,使用三
甲基氯硅烷时均无法观察到[11C]甲酯的形成。
这种方法是使用碱存在下[11C]
碘甲烷的替代方案。它特别适合于那些含官能团,会与[11C]
碘甲烷竞争的
羧酸,从而无需引入保护基团。然而,
邻茴香酸由于
甲醚的
水解断裂,形成了[11C]甲基
水杨酸酯,其衰减校正后的放射
化学产率为33-30%,而所需的[11C]甲基2-
甲氧基苯甲酸酯则无法获得。当使用
水杨酸作为起始物质时,[11C]甲基
水杨酸酯的衰减校正放射
化学产率仅为5-8%。版权所有 © 2004 John Wiley & Sons, Ltd。