Dihydro-3-(3-pyridoyl)-2-(3H)-furanone-d4 is an intermediate in the synthesis of 1-(3-Pyridyl-d4)-1,4-butanediol (P992504). 1-(3-Pyridyl-d4)-1,4-butanediol is the labeled analogue of 1-(3-Pyridyl)-1,4-butanediol (P992500), a metabloite of NNK (M325750), a carcinogen that readily produces cancer in rats and hamsters.