Tyrosinase-catalyzed oxidation of 3,4-dihydroxyphenylglycine.
The oxidation chemistry of dopa in relation to melanin biosynthesis has been extensively studied. However, the oxidation of its lower homolog viz., 3,4-dihydroxyphenylglycine has not been described. Using 3,4-dimethoxybenzaldehyde as the starting material, the chemical synthesis of 3,4-dihydroxyphenylglycine was accomplished by Strecker's synthesis and demethylation reactions. Tyrosinase readily oxidized this unusual amino acid to the expected quinone. The glycyl-o-benzoquinone thus formed was highly unstable like its higher analog, dopaquinone. However, unlike its counterpart, it failed to exhibit intramolecular cyclization reaction. Rather, glycyl-o-benzoquinone exhibited facile transformation(s) to ultimately generate 3,4-dihydroxybenzaldehyde as an isolatable product. A probable mechanism involving intermediary formation of unstable quinone methide and carbinolamine intermediates is proposed to account for the novel transformation of glycyl-o-benzoquinone to 3,4-dihydroxybenzaldehyde.
Sugumaran
M
M
Department of Biology, University of Massachusetts at Boston 02125, USA.
Tan
S
S
Sun
H L
HL
D001547:Benzaldehydes / Q000378:metabolism; D002396:Catechols / Q000138:chemical synthesis / Q000378:metabolism*; D003641:Deamination; D005998:Glycine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D008956:Models, Chemical; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D013053:Spectrophotometry
D001547:Benzaldehydes; D002396:Catechols; C099561:3,4-dihydroxyphenylglycine; C005581:protocatechualdehyde; D014442:Monophenol Monooxygenase; D005998:Glycine