Lanthanide ions play a major role in selective monoacylation of diols in water by benzoyl methyl phosphate (BMP). Their role is via a mechanism of internal addition from the conjugate base of bis-bidentate complex of diol, BMP and lanthanum ion. We have shown that this mechanism of lanthanum catalysis is also applicable to nucleosides, nucleotides and dinucleotides for their selective monoacylation with aminoacyl ethyl phosphates. Derivatives of nucleosides and nucleotides lacking the diol moiety are unreactive. The monoacylation of 2'- or 3'-hydroxyl group of nucleosides and nucleotides, with no reaction at 5'-hydroxyl group or phosphate group, shows high selectivity. The role of lanthanum in the highly selective acylation of diols by aminoacyl phosphate in aqueous solutions can serve as biomimetic analogy to the enzymic acylation of tRNA with various aminoacyl adenylates.