Minor Strecker degradation products of phenylalanine and phenylglycine

Phenylalanine (Phe) was oxidized with either potassium peroxodisulfate or g lyoxal. Volatile reaction products were isolated and analyzed by GC/FID and GC/MS. Nonvolatile products were derivatized with diazomethane and analyze d by the same methods. Under the experimental reaction conditions (equimola r ratio of reactants, 100 degreesC, 1 h), the decomposed amount of amino ac id was 28% (glyoxal) and to 74% (peroxodisulfate), respectively. Sixteen vo latile compounds having their origin in the amino acid molecule were detect ed and identified. The major compound was phenylacetaldehyde (208 mg/peroxo disulfate, 11 mg/glyoxal), followed by bibenzyl, benzaldehyde, and benzyl a lcohol. Other products were present in concentrations lower then 0.1 mg. Fo r comparison, the lower homologue of Phe, phenylglycine, was oxidized under the same conditions. Analogously, 21% (glyoxal) and 65% (peroxodisulfate) of this amino acid decomposed, predominantly to benzaldehyde (242 mg/peroxo disulfate, 95 mg/glyoxal). A minor decomposition product was benzoic acid ( 2.9 mg), other ten products arose at levels lower then 0.1 mg. The formatio n of minor oxidation products during Strecker degradation of amino acids su ggests the importance of radical reactions. In systems comprising glyoxal, ten heterocyclic compounds arose as minor products (3-furancarbaldehyde, 5- methyl-2-furancarbaldehyde, 2-pyrrolcarbaldehyde, 3-phenylpyridine, pyrazin e, methyl-, ethyl-, vinyl-, and 2-phenylethylpyrazine).