ガスクロマトグラフィー-マススペクトロメトリー(GC/MS)によるプロスタノイド分析のための Diethylhydrogensilyl-Cyclic Diethylsilylene (DEHS-DES) 誘導体 (第2報) : GC 及び GC/MS におけるトロンボキサンB<SUB>2</SUB> Methyl Ester-Methyloxime-DEHS-DES 誘導体の挙動

Abstract

A diethylhydrogensilyl-cyclic diethylsilylene (DEHS-DES) derivative of thromboxane B2 (TXB2) methyl ester-methyloxime was prepared by treating with diazomethane, O-methylhydroxyamine and then with N, O-bis(diethylhydrogensilyl)trifluoroacetamide. The gas chromatogram of the reaction product showed a well-resolved doublet when analyzed using a 5% phenylmethylsilicon-cross linked fused silica capillary column, being considered to correspond to syn- and anti-isomers. These components gave the ion of m/z 269 as a base peak or prominent peak and many characteristic ions which reflected the TXB2 system with moderate intensity. The ion of m/z 269 consists of the fragment of DES ring moiety and the α-side-chain. The mass spectrum (MS) of the second eluting component was considerably more complex than that of the first one. Almost all of the fragment ions in the MS of the first eluting component were also observed as characteristics common to the second eluting component. This ion made it possible to utilize internal standards for gas chromatography-selected ion monitoring (GC/SIM), which have been synthesized with deuterium (atom) labels at α-side-chain. Cl(NH3)-MS of these components were much simpler than the corresponding electron impact-MS, and they gave the protonated molecular ion with low intensity and the characteristic fragment ion of [MH-DEHSOH]+ (m/z 480) as the base peak. The 6-keto-PGF1α methyl ester-methyloxime-DEHS-DES derivative has the same molecular weight as the corresponding derivative of TXB2, but its MS is considerably more simple and lacks an ion of m/z 269 which is typical of aldehydic unit of TXB2 system. This 6-keto-PGF1α derivative gave a base peak at m/z 157, which was formed by the cleavage of F-prostaglandin ring system with a migration of hydrogen atom at C-10 to C-12. When GC/HR-SIM was carried out at the resolution power of 8000 by monitoring the ion of m/z 269.1573 which was specific for GC/SIM as structural integrity of TXB2, the SIR of its 25 pg of present derivative showed a well-resolved doublet with S/N of more than 300. These facts strongly indicates that the present derivative may be useful for the microanalysis of TXB2 by GC/SIM in biological materials.