Conversion of Cyclic Ribose to Acyclic Ribose under Prebiotic Conditions: Implications for Ribose Selection as the RNA Sugar

The RNA World hypothesis depicts the abiotic formation of RNA as the key milestone for the origin of life. However, the basis for the selection of ribose as the RNA sugar from the prebiotic context has not been explored in great detail. Leveraging on the classical organic chemistry knowledge that the acyclic form is the most reactive form of the sugar, we hypothesize that acyclic formation under prebiotic conditions is one of the primary pathways that led to the selection of ribose as the RNA sugar. As credible proof for our hypothesis, we identified prebiotically plausible catalysts [Bentonite/CaCO3/Mg(OH)2] and conditions to achieve the acyclic form in ribose compared to several other pentoses and hexoses. In this paper, evidence for the preferential formation of the acyclic form in ribose among the pool of sugars under prebiotic conditions is revealed. The results reported in this work suggest that the ability of ribose to exist in the acyclic form is unique among the pentoses and hexoses, which could have led to its selection as the RNA sugar.