Today, research in the RNA world is a medium-sized industry
At some point at the origin of life, RNA is thought to have had a catalytic role and to have functioned as the sole purveyor of genetic information–. However, until recently, there has been no demonstration of a prebiotically plausible synthesis of ribonucleotides to support this contention. It had long been thought that nucleobases and ribose should first be formed separately and then conjoin by glycosidation to give nucleosides that could then undergo phosphorylation, but there were two major problems with this approach. First, the oxygenous chemistry assumed necessary to make sugars seemed incompatible with the nitrogenous chemistry needed to make nucleobases, thus requiring either a spatial separation of the two chemistries followed by a bringing together of the products, or some sort of temporal separation. Second, it had not been possible to demonstrate the ribosylation of the canonical pyrimidine nucleobases, and the ribosylation of purines was very low yielding and gave many isomeric products. We wondered if a mixed oxygenous and nitrogenous chemistry might be synthetically productive if phosphate were included to catalyse certain reaction pathways. Accordingly, we explored mixed systems containing pentose and nucleobase precursor fragments as well as phosphate. This exploration resulted in our discovery of a phosphate-catalysed reaction in which a pentose fragment reacts with a pyrimidine nucleobase fragment to give an intermediate already having the C–N bond destined to become the glycosidic bond of a pyrimidine ribonucleotide. Subsequent reaction of this intermediate with the remaining pentose and pyrimidine nucleobase fragments gave an anhydronucleoside, which then underwent reaction with phosphate to give an activated pyrimidine ribonucleotide. To extend this synthesis back to simple prebiotic feedstock molecules requires compatible chemistry that furnishes pentose and nucleobase precursor fragments. This Article is concerned with the synthesis of the requisite pentose fragments—two- and three-carbon sugars.
Problems with the Natural Chemical "Origin of Life" …
A recent synthesis of activated pyrimidine ribonucleotides under prebiotically plausible conditions relied on mixed oxygenous and nitrogenous systems chemistry. As it stands, this synthesis provides support for the involvement of RNA in the origin of life, but such support would be considerably strengthened if the sugar building blocks for the synthesis—glycolaldehyde and glyceraldehyde—could be shown to derive from one carbon feedstock molecules using similarly mixed oxygenous and nitrogenous systems chemistry. Here, we show that these sugars can be formed from hydrogen cyanide by ultraviolet irradiation in the presence of cyanometallates in a remarkable systems chemistry process. Using copper cyanide complexes, the process operates catalytically to disproportionate hydrogen cyanide, first generating the sugars and then sequestering them as simple derivatives.
Powner et al., "Synthesis of activated pyrimidine ribonucleotides in prebiotically plausible conditions" [abstract | Editor's Summary], doi:10.1038/nature08013, p 239-242 v 459, Nature; and commentary by Jack W.