Dihydrouridine
Dihydrouridine (abbreviated as D, DHU, or UH2) is a pyrimidine which is the result of adding two hydrogen atoms to a uridine, making it a fully saturated pyrimidine ring with no remaining double bonds. D is found in tRNA and rRNA molecules as a nucleoside; the corresponding nucleobase is 5,6-dihydrouracil.