No abstract

No abstract

Analysis of the trimethylsilyl derivatives of adenosine and AMP with fast atom bombardment mass spectrometry provides structural information not observed in the fast atom bombardment spectra of the free compounds. The fast atom bombardment spectra of the trimethylsilyl derivatives is very similar to the electron impact spectra in the apparent presence of numerous odd-electron ions.tures are assumed to be the same as those proposed for the nucleoside3 and nucleotide4 TMS derivatives. d *The TMS, derivative is the major species observed in FAB; the TMS, is observed in some cases. The TMS, derivative is the major species present in El.Other ions in the FAB spectrum: m/z856(

The effect of trimethylsilyl (TMS) derivatization on detection limits of mononucleotides in fast atom bombardment-mass spectrometry (FAB-MS) was examined. FAB-MS methods were developed to optimize sensitivity using adenosine 5'-monophosphate as a model compound and then applied to reference standards of two clinically important nucleotides: tricyclic nucleoside-5'-monophosphate (TCNMP) and 5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP). The detection limit for the TMS derivative of TCNMP was 2.5-5 ng/microliters and less than 2.5 ng/microliters for FdUMP as its TMS derivative. This is greater than two orders of magnitude more sensitive than the FAB-MS analysis of the corresponding free compounds. These low detection limits for the TMS derivatives were obtained using a narrow scan range, signal averaging, detection in the negative ion mode, and 3-nitrobenzyl alcohol as the matrix. Hydrolysis of one or more of the labile TMS groups did occur, with the extent of hydrolysis being greatest in the more protic matrices.

The fast atom bombardment (FAB) mass spectra of bouvardin (1) 6-O-methylbouvardin (2), deoxybouvardin (3) and a synthetic analog (4) have been examined. The spectra of the bicyclic compounds 1-3 display site-directed fragmentations resulting from the presence of a phenolic bridged tyrosine moiety unique to this class of compounds. Comparison of the spectrum of 4, which lacks the rigid 14-membered ring, with the spectra of 1-3 shows some similarities, but clearly does not cleave in a site-directed manner as the other bouvardin analogs. Fragmentation pathways are postulated which account for most of the major ions observed in the FAB mass spectra of these potentially useful antitumor agents. Metastable ion analysis confirms the operation of the proposed pathways.