STUDY OF THE INTERACTION OF DINUCLEOTIDE ANALOGS WITH ALKALINE-EARTH METAL-IONS BY FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY

The fast atom bombardment (FAB)mass spectra of a series of dinucleotid e analogs, compounds 1-8 with alkaline earth metal chlorides (CaCl2, M gCl2, SrCl2 and BaCl2) were studied in a thioglycerol matrix. The posi tive-ion FAB mass spectra of 1-8 with CaCl2 gave [M + Ca - H](+), [M CaCl](+) and [M + Ca2Cl - 2H](+) ions. The formulae of [M + Ca - H]() and [M + Ca2Cl - 2H](+) ions from 2 were confirmed with high-resolut ion measurements. Compounds 1-8 with alkaline earth metal ions also gi ve metal chelated dimerized species [2M + Ca3Cl - 4H](+), [2M + Ca-2 - 3H](+) and [2M + Ca - H](+)], a process which is independent of the s ize of the polyether chain. The negative-ion FAB spectra also produce bimetallic ions with all substrates studied. Experiments with D2O addi tion using CaCl2 with compounds 2 and 6 suggested the elimination of a cidic protons (amide and/or amine) in the formation of [M + Met(x)Cl(y ) - nH) ions in either positive or negative modes. The site of the met al chelation was the same in both positive-and negative-ion mass spect ra. The collision-activated dissociation data suggest the covalent bon ding of the metal to the nitrogen base and coordination with the polye ther chain.