Figure 15.

Oxidation of transformations of 3,4-dihydroxyphenethyl alcohol. Tyrosinase (A) catalyzes the oxidation of 3,4-dihydroxyphenethyl alcohol to its quinone, which can undergo either enzyme catalyzed isomerization or nonenzymatic isomerization (B) to its quinone methide. Water addition to this quinone methide and reoxidation of 3,4-dihydroxyphenyl glycol and yet another isomerization produces a transient quinone methide that readily yields 2-hydroxy-3,4-dihydroxy acetophenone as the final product.