Inhibition of pig kidney L-aromatic amino acid decarboxylase by 2,3-methano-m-tyrosines

Both racemic (E)- and (Z)-2,3-methano-m-tyrosines (9E and 9Z) have been synthesized from a common intermediate, monoester (Z)-1-(ethoxycarbonyl)-2-[3-[(2-methoxyethoxy)methoxy]phenyl] cyclopropanecarboxylic acid (5). Quinine and ephedrine, respectively, were used to resolve their N-tert-butoxycarbonyl (Boc) derivatives. Among the compounds prepared, the (+)-(E)-diastereomer of 9 is the most potent inhibitor of L-aromatic amino acid decarboxylase (Dopa decarboxylase), having a Ki of 22 microM, with the (-)-Z-diastereomer (9Z) second at Ki = 49 microM. (+)-9E is a 45-fold more potent inhibitor of DDC than its acyclic analogue, D-m-tyrosine.