Fig. 7. Proposed mechanism of Fe³⁺-mediated protection of 1 from hydrolysis. In the absence of Fe³⁺, the phenol groups of the catechol moiety are able to enhance the attack of water on the β-lactone carbonyl. In the presence of Fe³⁺, the deprotonated catecholate coordinates the Fe³⁺ ion, effectively preventing hydrolytic breakdown of the lactone.