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The kinetics of nucleophilic substitution reactions involving 2,4‐dinitrophenyl 5‐substituted‐2‐thiophenecarboxylate were studied kinetically with 4‐Z‐C6H4O−/4‐Z‐C6H4OH, which facilitated the reactions, in 20 mol% DMSO(aq). The reactions followed second‐order kinetics and exhibited βacyl = −2.34 to −2.92, ρ(Y) = 2.71–3.39, βnuc = 0.74–0.83, and |βlg| = 0.40–0.57. Based on the interpretation of the results, we have concluded that the reaction follows an addition–elimination mechanism in which the first step is the rate‐determining step (rds). The transition state structures for the 4‐ZC6H4O−‐promoted reactions remained nearly the same with a change in the leaving group from 4‐nitrophenoxide to 2,4‐dinitrophenoxide. The mechanism of the 4‐ZC6H4O−‐promoted reaction was similar to that of R2NH‐promoted reactions, except that the former proceeded with the 1st step being the rds and the latter proceeded with a change in the rds from the second to the first step with a stronger nucleophile. [ABSTRACT FROM AUTHOR]

Phlorofucofuroeckol‐A (PFF‐A) is a phlorotannin extracted from various brown algae. PFF‐A shows low toxicity when ingested and various biochemical effects, including antioxidant, anti‐inflammatory, anti‐cancer, and anti‐allergy properties. In this study, various di‐O‐substituted PFF‐A derivatives were synthesized by introducing alkyl or acyl groups at two specific hydroxyls out of the nine nearly equivalent phenolic OH groups present in PFF‐A. The exact molecular structures of the synthesized derivatives were analyzed using two‐dimensional nuclear magnetic resonance (2D NMR) spectroscopy, which confirmed that the substituents were regioselectively introduced at the 1OH and 6OH positions. Small amounts of three mono‐O‐substituted derivatives were generated as by‐products in this reaction, and their structures and regioselectivity were determined using 2D NMR spectroscopy. This study can provide insights into understanding the mechanism of action of eckol‐based compounds and developing new drug candidates. [ABSTRACT FROM AUTHOR]

Reactions of 4‐nitrophenyl 2‐furoates (1a–e) with R2NH/R2NH2+ in 20 mol% DMSO(aq) have been studied. The reactions produced aminolysis products and exhibited second‐order kinetics. The Brönsted plots were linear with βnuc values of 0.75–0.89, which remained nearly the same for all 5‐furyl substituents. The rate data showed excellent correlations on the Yukawa‐Tsuno plots with ρ(x) = 0.72–1.1, and r = 0.55–0.95, respectively. The ρ value increased and r value decreased with a stronger nucleophile, indicating an increase in the electron density at the CO bond and a decrease in the resonance contribution. The results have been interpreted with the addition–elimination mechanism in which the second step is the rds. By comparing with the data for ArC(O)OC6H4‐4‐NO2 (Ar = Ph, thienyl), the effect of the aryl group on the acyl transfer reaction was assessed. [ABSTRACT FROM AUTHOR]

Microtubules play a dynamic role during cell division. In our early studies 4‐phenyl‐1‐(1‐acylindoline‐5‐sulfonylimidazolones were thoroughly explored and found that the indoline bicyclic system next to the sulfonyl group is very important for cytotoxicity. In this research, imidazolone motif was replaced with pyrrolidin‐2‐one and this isosteric replacement led to show some promising activity. Thus, the structure activity relationship of 4‐phenyl‐1‐(1‐acylindolin‐5‐ylsulfonyl)pyrrolidin‐2‐ones with the various acyl group at the indoline NH was explored. The presence of benzoyl groups with electron donating group was the more favorable for cytotoxicity while less bulky alkanoyl groups led to decrease cytotoxicity. [ABSTRACT FROM AUTHOR]