Thioester-mediated chemoselective aminoacylation of RNA in water.

Selective aminoacylation of RNA in water is a key challenge that must be resolved to elucidate the origin of peptide biosynthesis. To date there are no chemical methods to effectively and selectively aminoacylate RNA-2′,3′-diols, with the breadth of proteinogenic amino acids, in water. Here we demonstrate that prebiotic nitriles, aminoacyl-adenylates and N-carboxyanhydrides all react with thiols (including enzyme-cofactors) to selectively yield aminoacyl-thiols, which in turn aminoacylate RNA in high yield and selectivity for 2',3'-diols. Broad sidechain scope for both thioester synthesis and aminoacylation are demonstrated, including Ala, Asp, Arg, Glu, Gln, Gly, His, Leu, Lys, Phe, Pro, Ser and Val. Asp reacts with high (kinetic) alpha-aminoacylation selectivity, even upon dual activation of alpha- and beta-carboxylates, and Glu gamma-aminoacylation is blocked by pyroglutamate formation. Arg-aminoacylation is catalysed and enhanced by unprecedented sidechain nucleophilic catalysis. Thioester formation suppresses amine coupling and native-duplex is shown to direct chemoselective 2′,3′-aminoacylation of RNA. Our results suggest an important role for thiol cofactors in RNA-aminoacylation prior to the evolution of proteinaceous synthetase enzymes.