Cavitation as a plausible driving force for the prebiotic formation of N9 purine nucleosides

Summary. For the RNA world hypothesis, the direct condensation between nucleobase and ribose to afford canonical nucleoside has been a formidable challenge in terms of regioselectivity. In this report, we demonstrate that cavitation, a frequently occurring energy-intensive phenomenon upon the collapse of bubbles, could be a plausible driving force to form the purine nucleosides directly from nucleobase and ribose with the desired regioselectivity. Under cavitation, the overall yield of N9 nucleosides increases compared with non-cavitation conditions, whereas the amount of the undesired ribosylamino isomers decreases. Plausible geochemical scenarios on primordial Earth are proposed that could facilitate enrichment of the desired N9 nucleosides. Under salt-free dry-wet conditions, much improved yield (7.2%) and selectivity (N9/ribosylamino = 0.45) of the N9 isomers are achieved compared with the classical routes.