Derivatives of wyosine are tricyclic bases found at nucleotide 37 of tRNA(Phe) in eukaryotes. The pathway of wybutosine synthesis begins with a templated guanosine residue and proceeds through 6 steps catalyzed by 5 enzymes: N1 methylation of guanosine, condensation of 1-methylguanosine with pyruvate to yield 4-demethylwyosine, addition of an aminocarboxypropyl group to yield yW-86, methylation of yW-86 to yield yW-72, methylation of yW-72 to yield yW-58, and methoxycarbonylation of yW-58 to yield wybutosine (reviewed in Young and Bandarian 2013, Perche-Letuvée et al. 2014). Wybutosine may further be modified by hydroxylation and methylation. Wyosine derivatives at position 37 of tRNAs participate in translational fidelity by stabilizing codon-anticodon pairing (Konevega et al. 2004) and preventing frameshifting (Waas et al. 2007).