A-2 Studies on the pyrolysis of amino acids

3-amino-l,4-dimethyl-5//-pyrido[4,3-b]indole (Trp-P-1) from tryptophan (3829) and 2-aminodipyrido[l,2-fl 3 ,2 -d]imida-zole (Glu-P-2) and 2-amino-6-methyldipyrido[l,2-fl 3 ,2 - (] imidazole (Glu-P-1) from glutamic acid (3828a, 4365a), all four of which were subsequently identified in tobacco smoke (3828c). Table XVII.A-2 catalogs many of the pyrolysis studies conducted on amino acids. 

Pyrolysis and smoke studies of amino acids indicate that they are potential precursors of several nitrogen heterocyclic ring systems found in tobacco smoke. Proline has been shown to be efficiently converted to pyrrole upon pyrolysis (3219, 3724) and in addition has been proposed as a possible precursor of pyrocoll (2593, 4336). y-Amino acids and dicarboxy-lic amino acids are capable, under pyrolytic conditions, of forming 2-pyrrolidones (1967, 3079) and by a similar mechanism, A-amino acids can form 2-piperidones (1967, 3079). A side effect of the pyrolysis of amino acids is the formation of hydrogen cyanide. 

Protein and free amino acids found in tobacco leaf contribute significantly through pyrodegradation and pyrosynthesis to the formation of many nitrogenous compounds found in tobacco smoke. The nonvolatility of these compounds either as free acids, proteins, or members of tobacco pigment, for example, porphyrins, make them particularly liable to pyrolytic destruction because they, unlike nicotine and the other plant alkaloids, are not readily volatilized and swept away as the more intense heat of the cigarette coal approaches (3724). 

There are also interactions that occur among amino acids, proteins, and carbohydrates during plant growth and during smoke formation. These interactions form complex mixtures of leaf constituents and complex mixtures resulting from the pyrodegradation and pyrosynthesis of reaction products of amino acids, proteins, and carbohydrates. 

Amino acids Kato et al. (2048, 2049), Kosuge etal. (2178a), Masudacia/. (2486), Nebert et al. (2688a) 

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