A study of metal chelation of dinucleotide analogs in the gas phase by fast-atom bombardment mass spectrometry

Abstract

Fast-atom bombardment (FAB) mass spectrometry was used to investigate the interaction of proton and alkali metal ions with dinucleotide analogs such as T-n-T (T = thymine moiety, n = polyether chain, e.g., triethylene, tetraethylene, pentaethylene, and hexaethylene ether 1-4), A-n-T (A = adenine unit 5-8), and T-n-OMe (9-12) in 3-nitrobenzyl alcohol matrix. The [M + H](+) ion is the most abundant ion for the A-n-T series, whereas in 1-4 and 9-12 the (TC2H4)(+) ion is the most abundant. Formation of [M + H -C2H4O](+) ions, a characteristic fragmentation of crown ethers under electron ionization, is observed for compounds 1-12 and is more pronounced in 6 and 7. An abundant [M - H](-) ion is observed for all the compounds studied under negative ion FAB due to the presence of the (-CO-NH-CO-) group of thymine, an indication of existence of intramolecular H bonding. The FAB mass spectra of 1-12 with alkali metal ions (Li(+), Na(+), K(+), Rb(+), and Cs(+)) showed formation of abundant metal-coordinated ions ([M + Met](+) and [TC2H4 + Met](+)). Compounds 3, 4, 6, 7, and 10-12 showed ions due to the substitution of the thymine moiety by a hydroxyl group ([M + Met - 108](+), Met = metal ion). For compound 3 alone, substitution of two thymine groups ([M + Met - 216](+)) was observed. Metastable ion studies were used to elucidate the structures of these potentially significant ions, and the ion formule were confirmed with high resolution measurements. Selectivity toward metal complexation with ligand size was seen in the T-n-T and A-n-T series and was even more pronounced in A-n-T series. These dinucleotide analogs fall in the following order of chelation of alkali metal ions, acyclic glymes < dinucleotide analogs (acyclic glymes substituted with nitrogen bases) < crown ethers, which places them in perspective as receptor models.

New 1,2,4-triazine-containing podands: synthesis and properties

“…[12][13][14] As should be expected, 1,2,4 triazin 5 ones exhibited a lower reactivity in the reactions with podands than 1,2,4 triazines 2 and 3, and no products of the reaction of triazines 6-8 with compound 1а in the presence of trifluoroacetic acid were found in a detector of the NMR spectrometer. This method differs substantially from those published previously for syntheses of podands of this type, which represented a ring closure of open chain structures and nucleophilic substitution of good leaving groups in a heterocycle.…”

Glymes as versatile solvents for chemical reactions and processes: from the laboratory to industry

“…The complex formation is a direct result of hydrogen bonding between carboxyl groups and crown ether- or glyme–oxygen atoms and also from hydrophobic interactions; such a precipitation is pH dependent. Saraswathi and Miller 152 studied the interaction of proton and alkali metal ions with dinucleotide analogs of acyclic polyethers using the fast-atom bombardment (FAB) mass spectrometry, and suggested the following order of chelation of alkali metal ions, acyclic glymes < dinucleotide analogs (acyclic glymes substituted with nitrogen bases) < crown ethers.…”

Complexation of transition-metal ions, SnII, PbII and Al III with nucleobase-substituted polyethers and dissociation of adduct ions studied by fast atom bombardment mass spectrometry

“…The FAB mass spectra of polyethers substituted with nucleobases showed the existence of intramolecular Watson-Crick interactions which are more effective between adenine and thymine than between thymine and thymine. 3 Metal ions play an important role in biological systems and are often required as cofactors for enzymes. The metalcomplexing properties of crown ethers have biological as well as chemical significance.…”