Phytochemical Studies on the Tobacco Alkaloids. XII. Identification of gamma-Methylaminobutyraldehyde and its Precursor Role in Nicotine Biosynthesis.

gamma-Methylaminobutyraldehyde (N-methylpyrroline) labeled with (14)C was isolated from tobacco roots which had metabolized ornithine-2-(14)C. It was labeled most strongly 4 hours after adding ornithine-2-(14)C to the root, also labeled by putrescine-1,4-(14)C and methionine-(14)CH(3), and observed in the root but not in the aerial portions of tobacco plants. gamma-Methyl-aminobutyraldehyde when added back to the root was an efficient precursor of nicotine. Identity of gamma-methylaminobutyraldehyde from tobacco roots was confirmed by comparison with the authentic compound.The existence of gamma-methylaminobutyraldehyde (N-methylpyrroline) in the biosynthetic pathway of nicotine indicates that the methyl group must be introduced before condensation of the pyridine moiety with the pyrrolidine moiety.