4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific nitrosamine, is believed to be important as a potent pulmonary carcinogen in smokers.NNK is extensively metabolized to its carbonyl reduction product 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), which is also a causative agent for lung cancer.Considering their chemical structures, the metabolism of NNK to NNAL produces a chiral center.It was reported that (R)-NNAL is more tumorigenic in mice than (S)-NNAL and that these enantiomers have substantially different metabolic pathways[1].