Current Organocatalysis - Online First

Drug-resistant microorganisms are a major concern, particularly as more strains develop resistance to various antimicrobial agents. Some microbes are currently immune to all antibiotics. Consequently, it is imperative to develop novel drugs that maintain their effectiveness. The benzimidazole nucleus can be found in a wide variety of heterocyclic compounds in nature. Numerous investigations have been conducted on the physiological effects of molecules containing this moiety.

Some more recent benzimidazole analogues were synthesized through the synthetic stages of o-phenylene diamine with 6-bromo-3,4-dihydro-2H-chroman-2-carboxylic acid, followed by various electrophiles, in the search for new antibacterial and antifungal compounds with improved efficacy. ¹H NMR, IR, and mass spectral data were used to determine the structures of these recently synthesized compounds. For their antibacterial and antifungal activities, all the produced compounds were tested. Besides their biological activities, these newly synthesized compounds were also docked into the active pocket of Dihydrofolate Reductase and Sterol 14-alpha demethylase to predict their binding modes concerning antibacterial and antifungal activities, respectively. Moreover, these predictions would be utilized for the exploration of the mechanism of action on selected enzyme subunits.

Synthesis of 2-(6-bromochroman-2-yl)-1H-benzo[d]imidazole (4a-4y) derivatives was done using the classical Philipins condition. Spectral analysis revealed their structures. Amongst the synthesized scaffolds (4a-4y), target compounds 4r and 4w were active when compared with ciprofloxacin. Compound 4j was found to be highly active compared to clotrimazole. Ligands 4w and 4e exhibited better binding energy on Dihydro Folate Reductase and Sterol 14-alpha demethylase (-7.1899 kcal/mol and -8.72613 kcal/mol) enzymes, respectively.

The current investigation may have shown that the produced compounds differ from one another, regardless of their structure or observable biological activity. In the quest for a new group of antibacterial and antifungal molecules, these compounds may be useful to society.

Ulvan, a sulfated polysaccharide derived from the green seaweed Ulva lactuca, is widely used in different industrial applications. However, achieving a high yield of ulvan requires an efficient extraction method. Mechanochemical-assisted extraction (MCAE) is an eco-friendly and effective technique commonly used for extracting natural products, including polysaccharides.

This study aims to extract ulvan using the MCAE method and optimizes the extraction conditions using the Box-Behnken design (BBD) of Response Surface Methodology (RSM).

The extraction parameters optimized included solid reagent concentration, milling time, solid/liquid ratio, extraction time, and temperature. Analysis of variance (ANOVA) was applied to assess the statistical significance of the model. Fourier transform infrared (FTIR) spectroscopy was performed to confirm the structural features of the extracted ulvan. Scanning electron microscopy (SEM) analysis revealed the morphological changes in Ulva lactuca before and after mechanochemical treatment.

The optimized extraction conditions were 36.33% solid reagent (Na2CO3), 29.75 minutes of milling time, a solid/liquid ratio of 1:24.98 (g/ml), an extraction time of 140.5 minutes, and a temperature of 80°C. Under these conditions, the extraction yield of crude ulvan was 29.28% ± 0.003, significantly higher than the yield obtained using the conventional acidic-hot water method (10.31% ± 0.16%). The statistical model was highly significant (p < 0.0001) with a high regression coefficient (R² = 0.9811).

The MCAE method proved to be a highly efficient and sustainable approach for extracting ulvan from Ulva lactuca, offering a significantly increasing yield and reducing extraction time compared to traditional methods.

The ester functional group is crucial in organic chemistry as well as in other fields due to its diverse applications. Thus, its synthesis in a simple and effective manner remains an interesting task. In literature, many one-pot reactions are reported for the transformation of carboxylic acid into ester. However, many of them are inapplicable due to their limitations, such as, longer reaction time, harsh reaction conditions, usage of expensive reagents, etc. Hence, a simple as well as effective transformation of carboxylic acid to ester is still desirable.

The study intends to develop a procedure for esterification reaction in a simple and cost effective manner under a mild reaction condition.

The demonstration reflects the activation of carboxylic acid employing a combination of triphenylphosphine and N-bromosuccinimide (NBS) at low temperatures. The activated carboxylic acid reacts with alcohol to form the corresponding ester. At elevated temperatures, the reaction can be completed at a faster rate, while at room temperatures the process is relatively slower and takes quite a long time.

Carboxylic acids (containing aromatic and heteroaromatic moieties) were made to react with different alcohols, and the desired esters were obtained quickly under optimum reaction conditions. Good to excellent yields of the desired esters were obtained in most of the reactions.

An ameliorated procedure for the esterification of carboxylic acid is reported. Activation of carboxylic acid was achieved using triphenylphosphine and NBS. The activated acid thus formed, upon reaction with various alcohols, produced the corresponding ester in good yields.