Cyclization step of noradrenaline and adrenaline autoxidation: a quantum chemical study

Selective electrophilic cyclization of ortho-carbonylarylacetylenols for the synthesis of cyclopenta[a]naphthalenol and 2-phenylnaphthalen-1-ol analogs

This work demonstrates a new method for the synthesis of cyclopenta[a]naphthalenol and 2-phenylnaphthalen-1-ol analogs via selective cyclization. ortho-Alkynylarylkenones were employed as the common substrates that could be prepared by Sonogashira coupling between 2-haloarylacetophenone and pent-4-yn-1-ol derivatives. These precursors were used without purification to construct 2-phenylnaphthalen-1-ol intermediates by treating with (+)-CSA under heating conditions. Selective cyclization occurred when the reaction was conducted in methyl trimethylacetate solvent which predominantly produced the 2-phenylnaphthalen-1-ol product through 6-endo-dig cyclization without elimination or the formation of cyclopenta[a]naphthalenol via shutting down the 5-exo-dig mode of cyclization. Switching the acid from a Brønsted acid to Bi(OTf)3 led to smooth reactions, providing the cyclopenta[a]naphthalenol products in moderate to good yields. Moreover, we also demonstrated the utilization of 2-phenylnaphthalen-1-ol to prepare naphthoquinone, which is an important core structure of bioactive and natural product compounds.

Antioxidant activity of lidocaine, bupivacaine, and ropivacaine in aqueous and lipophilic environments: an experimental and computational study

Introduction: Local anesthetics are widely recognized pharmaceutical compounds with various clinical effects. Recent research indicates that they positively impact the antioxidant system and they may function as free radical scavengers. We hypothesize that their scavenging activity is influenced by the lipophilicity of the environment. Methods: We assessed the free radical scavenging capacity of three local anesthetics (lidocaine, bupivacaine, and ropivacaine) using ABTS, DPPH, and FRAP antioxidant assays. We also employed quantum chemistry methods to find the most probable reaction mechanism. The experiments were conducted in an aqueous environment simulating extracellular fluid or cytosol, and in a lipophilic environment (n-octanol) simulating cellular membranes or myelin sheets. Results: All local anesthetics demonstrated ABTS˙⁺ radical scavenging activity, with lidocaine being the most effective. Compared to Vitamin C, lidocaine exhibited a 200-fold higher half-maximal inhibitory concentration. The most thermodynamically favorable and only possible reaction mechanism involved hydrogen atom transfer between the free radical and the -C-H vicinal to the carbonyl group. We found that the antioxidant activity of all tested local anesthetics was negligible in lipophilic environments, which was further confirmed by quantum chemical calculations. Conclusion: Local anesthetics exhibit modest free radical scavenging activity in aqueous environments, with lidocaine demonstrating the highest activity. However, their antioxidant activity in lipophilic environments, such as cellular membranes, myelin sheets, and adipose tissue, appears to be negligible. Our results thus show that free radical scavenging activity is influenced by the lipophilicity of the environment.