5-[4-(Methylnitrosoamino)-1-oxobutyl]-2(1H)-pyridinone; 1-(1,6-Dihydro-6-oxo-3-pyridinyl)-4-(methylnitrosoamino)-1-butanone; 4-(Methylnitrosamino)-1-[3-(6-hydroxypyridyl)-1-butanone; 5-[4-(Methylnitrosoamino)-1-oxobutyl]-2(1H)-pyridinone; 6-Hydroxy-NNK