作者:Charles S. Elmore、Dennis C. Dean、Yong Zhang、Carter Gibson、Herb Jenkins、Allen N. Jones、David G. Melillo
DOI:10.1002/jlcr.537
日期:2002.1
Stable label analogues of methotrexate (MTX) and 7-hydroxymethotrexate (7-OH-MTX) were required for use as internal standards for LC/MS quantitation. A minimum incorporation of stable isotopes to produce a mass increase of 3 in the non-glutamate derived portion of the molecule was necessary for adequate MS detection. The commercial availability of des-methyl MTX (aminopterin, 1) made methylation with C2H3I an attractive option. Surprisingly, all attempted methylations of 1 and the dimethyl ester of 1 failed to provide a significant amount of the methylated aniline, apparently due to attenuated reactivity of the secondary amine towards alkylation. However, reductive amination of diacid 1 with C2H2O and NaB2H3CN gave [C2H3]MTX in 52% yield. A previously reported method was utilized to convert [C2H3]MTX to [C2H3]7-OH-MTX. Preparative HPLC purification of [C2H3]7-OH-MTX resulted in extremely low recovery from the column; this was resolved by switching to a column with few free silanols. Copyright © 2002 John Wiley & Sons, Ltd.
需要甲氨蝶呤(MTX)和7-羟甲基甲氨蝶呤(7-OH-MTX)的稳定同位素标记类似物作为LC/MS定量的内标。为确保足够的MS检测,分子中非谷氨酸部分至少需引入稳定同位素使其质量增加3。由于去甲基MTX(氨基蝶呤,1)的商业可用性,使用C2H3I进行甲基化成为一种吸引人的选择。令人意外的是,1及其二甲酯的所有甲基化尝试均未能提供显著量的甲基化苯胺,显然是由于二级胺对烷基化的反应活性减弱。然而,二酸1与C2H2O和NaB2H3CN的还原胺化反应以52%的产率得到了[C2H3]MTX。先前报道的方法被用于将[C2H3]MTX转化为[C2H3]7-OH-MTX。[C2H3]7-OH-MTX的制备型HPLC纯化导致柱回收率极低;通过切换到含少量自由硅醇的柱得以解决。版权所有 © 2002 John Wiley & Sons, Ltd.