RNA Sugars May Have Had Cyanide Origins

The primeval recipe for RNA’s sugar components likely started with hydrogen cyanide, not formaldehyde as researchers had thought (Nat. Chem., DOI: 10.1038/nchem.1467). John D. Sutherland of the Medical Research Council Laboratory of Molecular Biology, in Cambridge, England, previously reported a route to ribonucleotides that would be plausible on an early Earth, supporting RNA’s involvement in the origin of life. But his team didn’t show how RNA’s sugar building blocks—glycolaldehyde and glyceraldehyde—could arise from one-carbon precursors. Most chemists cite the formose reaction, an oligomerization of formaldehyde, as the source of prebiotic sugars. But that reaction yields messy product mixtures. Sutherland and postdoc Dougal Ritson now suggest an alternative pathway inspired by a century-old sugar synthesis. They exposed an aqueous solution of hydrogen cyanide and copper cyanide to UV light and observed oxazolidinones as major products. Those compounds “are a smoking gun” for the sugars, Sutherland says. Cyanate formed in the reaction traps the sugars in their oxazolidinone forms as they are generated, he explains. The researchers are now trying to replace copper with iron, because iron’s redox properties should prevent cyanate formation, leading to free sugars.