Synthesis and Degradation of Nucleobases and Nucleic Acids by Formamide in the Presence of Montmorillonites.

We describe the role of formamide, a product of the hydrolysis of hydrogen cyanide, as precursor of several components of nucleic acids under prebiotic conditions. When formamide is heated in the presence of montmorillonites, the efficient one pot synthesis of purine, adenine, cytosine, and uracil is obtained. Along with these nucleobases, several components of the inosine pathway are obtained: 5-aminoimidazole-4-carboxamide, 5-formamido-imidazole-4-carboxamide and hypoxanthine. This almost complete catalogue of nucleic acid precursors is accompanied by N-9-formylpurine, which, containing a masked glycosidic bond in its formyl moiety, is a plausible precursor of purine acyclonucleosides. In addition, montmorillonites differently affect the rate of degradation of nucleobases with embedded in 2'-deoxyoligonucleotides; namely, montmorillonites protect adenine and guanine from the degradative action of formamide, while thymine degradation is enhanced. The oligonucleotide backbone reactivity to formamide is also affected; this shows that the interaction with montmorillonites modifies the rate of abstraction of the Halpha and Hbeta protons on the sugar moieties.