Fast atom bombardment combined with tandem mass spectrometry for the study of dinucleotides

A study of mono- and dinucleotides by utilizing negative ion fast atom bombardment (FAB), metastable decomposition of (M-H)- species, and collisionally activated decomposition (CAD) of (M-H)- species is reported. Data were obtained for several complete series containing the standard nucleosides (guanosine, adenosine, cytidine, thymidine, and uridine): the 3'- and 5'-monophosphate mononucleotide series for both ribo- and 2'-deoxyribomononucleotides, all possible combinations for the 3'(-)----5'-ribodinucleotides, and all possible combinations of the 3'(-)----5',2'-deoxyribodinucleotides. The metastable and CAD spectra provide more information than the FAB mass spectra. The (M-H)- ions of all dinucleotides decompose either as metastable ions or upon collisional activation to eliminate BH (B = base) preferentially from the 3'- rather than the 5'-terminus. Isomeric dinucleotides can be distinguished on the basis of this fragmentation. To establish the identity of the base at the 5'-terminus, collisional activation is preferred. By comparing relative abundances of BH elimination observed, the inherent basicities of the nucleoside base anions can be inferred to be C- greater than A-, T-, greater than G-.

N-hydroxymethyl derivatives of nitrogen heterocycles as possible prodrugs I: N-hydroxymethylation of uracils

Solid samples of 1,3-dihydroxymethyluracil, 3-hydroxymethyl-1-methyluracil, and 1-hydroxymethyl-3-methyluracil were prepared, and their structures were confirmed by spectroscopic analysis. The thermodynamics and kinetics of the formation of N-hydroxymethylated uracils in aqueous formaldehyde solutions also were studied. The equilibrium constants for formation of N-1-hydroxymethyl derivatives were approximately twice those for formation of N-3-hydroxymethyl derivatives, and they were formed more rapidly throughout the pH 3--8 range. Substituents at C-5 of uracil had little effect on the thermodynamics of N-hydroxymethylation. The potential usefulness of N-hydroxymethyl compounds as prodrugs is discussed.