The chemical reactions and pathways resulting in the formation of wybutosine, 3H-imidazo[1,2-alpha]purine-7-butanoic acid, 4,9-dihydro- alpha-[(methoxycarbonyl)amino]- 4,6-dimethyl-9-oxo- 3-beta-D-ribofuranosyl methyl ester, a modified nucleoside found in some tRNA molecules. (Gene Ontology, GO_0031591)
