NATURE OF THE SPECIFIC INTERACTION OF RHODIUM ACETATE DIMER WITH ADENOSINE

Rhodium acetate dimer [Rh2(Ac)4(H2O)2] reacts specifically with adenos ine and not with guanosine, cytidine, or uridine. NMR studies have bee n conducted in DMSO solution to elucidate the structural basis for thi s specificity. By the use of various analogues, it was shown that neit her N-7 nor N-1 binding can account for the formation of the complex b etween the rhodium atoms and adenosine in DMSO solution [although the former has been demonstrated in crystals of 1-methyl adenosine with th e dimer (from water and methanol) ]. NMR line broadening of C-2, C-6, and C-8, but not of C-4 and C-5, is in line with pi-bonding, A Huckel calculation demonstrates that the former atoms exhibit electron densit y maxima. The effects of various analogues of adenosine are also in li ne with pi-bonding. Since guanosine is a poorer pi-acceptor, its inabi lity to react in the manner of adenosine can be explained. The rhodium acetate dimer, unlike the previously studied copper acetate dimer, do es not react with the ribose hydroxyl groups of nucleosides. It there fore does not differentiate between ribo- and deoxynucleosides, but is a potential probe of nucleic acid structure by virtue of its base spe cificity.