Formation of nucleosides and nucleotides in chemical evolution

Nucleosides and nucleotides are important biomolecules. Following Gilbert's (Nature 319:618, 1986) proposal of an "RNA world, " various processes for the formation of nucleosides (from nucleobases and ribose) and the polymerization of nucleotides have been suggested. Problems associated with the formation of RNA have also been pointed out. The constituents of RNA are nucleobases, ribose, and phosphate. Ribose has five conformational isomers or conformers, each of which can react with a nucleobase. In life, however, only the β-furanose form of ribose is used. Curiously, when a nucleobase reacts with ribose in an aqueous solution, only a small amount of nucleoside with a β-ribofuranose component is detectable in the total products. Thus, the RNA world hypothesis has reached a deadlock. Here, we summarize the important points in the synthesis of nucleobases and ribose. We also describe the selective formation of nucleosides and touch on the one-pot synthesis of nucleotides.