Direct Prebiotic Pathway to DNA Nucleosides
Angewandte Chemie International Edition https://doi.org/10.1002/ange.201903400
It is assumed that RNA played a key role in the origin of life. The hypothesis of the RNA world is that the transition to more complex but more stable DNA for continuous information storage and replication requires the development of a ribonucleotide reductase to obtain the deoxyribonucleotides from ribonucleotides. This step, as well as an alternative path from abiotic molecules to DNA-based life, is completely unknown. Here we show that deoxyribonucleosides are formed under relevant prebiotic conditions in water in high regio- and stereoselectivity from all canonical purine and pyrimidine bases by condensation with acetaldehyde and sugar-forming precursors, e.g. formaldehyde, glycolaldehyde and glyceraldehyde. We can explain the origin and selection of deoxyribose versus other deoxysugars during nucleoside formation. Thus, we have found a continuous path to DNA nucleosides, starting from simple, prebiotically available molecules. Furthermore, we identified the deoxyapionucleosides (DApiNA) as a further potential DNA progenitor. Our results allow to conclude that the DNA world evolved much earlier than previously assumed.