气相中2-甲氧基乙酸参与9-芴甲氧羰基脱除反应的质谱研究  

Mass Spectrometric Study on 9-Fluorenylmethyloxycarbonyl Group Removal Assisted by 2-Methoxyacetic Acid in Gas Phase

作　　者：高校飞 姚泽华 董茂友 陈祥钊 GAO Xiao-fei;YAO Ze-hua;DONG Mao-you;CHEN Xiang-zhao(Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation,School of Chemistry and Materials Science,East China University of Technology,Nanchang 330013,China;Key Laboratory of Prevention and Treatment of Cardiovascular and Cerebrovascular Diseases of Ministry of Education,Gannan Medical University,Ganzhou 341000,China)

机构地区：[1]东华理工大学化学与材料学院,江西省质谱科学与仪器重点实验室,江西南昌330013 [2]赣南医学院,心脑血管疾病防治教育部重点实验室,江西赣州341000

出　　处：《质谱学报》2024年第2期246-255,共10页Journal of Chinese Mass Spectrometry Society

基　　金：国家自然科学基金(22204017);江西省质谱科学与仪器重点实验室开放基金(JXMS202115);赣南医学院科研启动基金(QD202119);江西省国际合作项目(20203BDH80W010)。

摘　　要：本研究主要探讨气相条件下,乙酸(HAc)、3-甲氧基丙酸(MPA)和2-甲氧基乙酸(MAA)在氨基酸保护基9-芴甲氧羰基(Fmoc)脱除过程中的作用。采用自制的纳喷装置将反应溶液依次雾化进入质谱仪,在线监测3种羧酸分别与不同氨基酸底物反应的关键离子,探讨羧酸与底物结构对复合物形成及质谱解离模式的影响。结果表明,对于同一氨基酸结合不同羧酸的复合物,只有相对含量较高的MAA复合物发生了解离。这可能是因为MAA 2号位的甲氧基促进了MAA与Fmoc基团9号碳上H的复合,降低了该H解离过渡态能垒,从而有利于MAA与Fmoc保护的氨基酸(X_(f),X_(f)=G_(f),A_(f),V_(f),L_(f),M_(f),F_(f),P_(f))形成的复合物[X_(f)+MAA-H]-阴离子中Fmoc的解离。对于MAA的不同氨基酸复合物而言,N上没有H的P_(f)复合物阴离子[P_(f)+MAA-H]-解离的碎片是以Fmoc脱除产物为主,其他氨基酸的MAA复合物则以丢失中性MAA碎片为主。可见,羧酸结构和氨基酸底物结构对复合物分子的形成和复合物分子中Fmoc的解离有着重要影响,该研究结果有助于理解气相中Fmoc解离的分子离子反应过程。The detachment of 9-fluorenylmethyloxycarbonyl(Fmoc)from the amino group is widely performed in chemical synthesis reactions,involving peptides,nucleosides,polymers and some other organic compounds.Reported methods for Fmoc release mainly referred to traditional bases.Limited information about carboxylic acid-participating Fmoc detachment has been documented.This study mainly investigated the role of acetic acid(HAc),3-methoxypropionic acid(MPA),2-methoxyacetic acid(MAA)in the process of Fmoc deprotection in gas phase.The home-made nano emitter was used to spray the mixed solution of the three carboxylic acids and different Fmoc protected amino acids,which flew into the inlet of mass spectrometer(MS),to monitor the key adduct ions derived from the reaction of carboxylic acids and protected amino acids,such as Gly,Ala,Val,Leu,Pro,Met and Phe.Furthermore,the effects of substrate structures on the formation of the adduct in MS and its dissociation in MS/MS were discussed.The results showed that the relative abundance of MAA adducts were significantly higher than that of HAc adducts and MPA adducts for the same Fmoc protected amino acid,and only MAA related adducts can dissociate into fragments with 20%collision energy(CE).This is due to the special structure of MAA,which has a methoxy group providing a lone pair of electrons to the acidic hydrogen at the second position of the carboxylic acid.Thus,the methoxy group weakly interacted with the H at the 9th position of Fmoc ring,promoting the formation of the adducts of MAA and Fmoc protected amino acid to decrease the energy barrier of the transition state for the 9th H release process.All the[X_(f)+MAA-H]-adducts can generate two kinds of successor ions upon 20%CE,one is the Fmoc removal fragment,another is only MAA loss fragment.Interestingly,[P_(f)+MAA-H]-mainly gave fragments of the Fmoc removal products,whereas the other six compounds with relatively low abundance ratio mostly produced fragments by neutral MAA loss.This difference of the fragmentation pathways ma

关 键 词：9-芴甲氧羰基(Fmoc) 脱保护 分子离子反应 质谱 

分 类 号：O657.63[理学—分析化学]