ABSTRACT
The laccase reactions proceed by formation of a radical cation, with subsequent deprotonation of the hydroxy group to give a radical. The highest yields of dimers type VI were recovered from the substrate 2,5-dihydroxy-N-(2-hydroxy-ethyl)-benzamide with antibacterial reaction partners, e.g., ampicillin, amoxicillin. The position of the linkage between the laccase substrate and the reaction partner is dependent on the character, position, and number of the substituents present on the substrate. In cases where both reaction partners are laccase substrates, the heteromolecular reactions are faster and more complex. Illustrative examples are the coupling reactions of mercapto structures with p-hydroquinone structures. para-Dihydroxy aromatic acids and their derivatives are structurally related to the ganomycins, a class of antibacterial compounds with a para-dihydroxy aromatic main structure. Various penicillin and cephalosporin derivatives result from laccase-mediated oxidation followed by nuclear amination of 2,5-dihydroxybenzoic acid derivatives. Amoxicillin and ampicillin were used as representatives of penicillins and cefadroxil, cefalexin, and cefaclor as examples of cephalosporins.
