Search Results (7)

One of the most important reactions in organic synthesis is esterification, and the compounds generated using this process are esters with a wide range of applications in various industries. Numerous approaches have been employed to enhance the ester yield and reaction rate and establish equilibrium in esterification reactions. This study uses a non-catalytic thermal esterification method to obtain unbranched aliphatic esters C4–C8. The effect of an audio frequency electric field instead of a catalyst on the esterification reaction between acetic acid and linear C4–C8 aliphatic alcohols was studied. The main goal of this study was to design and implement a lab-scale device for the synthesis of aliphatic esters in an environmentally sustainable manner using only specific raw materials and an audio frequency electric field at 3 and 6 kHz at 20 °C and 50 °C. A mechanism for the esterification reaction using an audio frequency electric field is also suggested. The proposed experimental device is designed to produce esters in a green and cost-effective manner and could be used on a large scale in the food, cosmetics, and pharmaceutical industries. Full article

Herein, we simultaneously prepared borax-crosslinked starch-based hydrogels with enhanced mechanical properties and self-healing ability via a simple one-pot method. The focus of this work is to study the effects of the amylose/amylopectin ratio of starch on the grafting reactions and the performance of the resulting borax-crosslinked hydrogels. An increase in the amylose/ amylopectin ratio increased the gel fraction and grafting ratio but decreased the swelling ratio and pore diameter. Compared with hydrogels prepared from low-amylose starches, hydrogels prepared from high-amylose starches showed pronouncedly increased network strength, and the maximum storage modulus increased by 8.54 times because unbranched amylose offered more hydroxyl groups to form dynamic borate ester bonds with borate ions and intermolecular hydrogen bonds, leading to an enhanced crosslink density. In addition, all the hydrogels exhibited a uniformly interconnected network structure. Furthermore, owing to the dynamic borate ester bonds and hydrogen bonds, the hydrogel exhibited excellent recovery behavior under continuous step strain, and it also showed thermal responsiveness. Full article

Biodiesel has established itself as a renewable fuel that is used in transportation worldwide and is partially or in some cases completely replacing conventional fuels. Chemically, biodiesel is a fatty acid monoalkyl ester (FAAE). Generally, the term biodiesel refers to the fatty acid methyl or ethyl esters (FAME or FAEE). Herein, an overview of the research on the synthesis of FAAE in which the alkyl moiety is a C₃₊ alkyl chain (branched/unbranched) is given. In addition, a comparison of the properties of the aforementioned FAAE with each other, with FAME and FAEE, and with fuel standards is given. The length of the alkyl chain has a major influence on viscosity, while pour point temperatures are generally lower when branched alcohols are used, but the fatty acid part of the molecule also has a major influence. The development of new pathways for the synthesis of higher alcohols from biomass opens a future perspective for the production of long chain FAAE as biofuels, fuel additives, or biolubricants. Due to their properties, FAAEs produced from C₃–C₅ alcohols have the potential to be used as fuels, while all C₃₊ FAAEs can be used as valuable bioadditives, and C₈₊ FAAEs can be used as biolubricants and viscosity improvers. Full article

For decades, various plants have been studied as sources of biologically active compounds. Compounds with anticancer and antimicrobial properties are the most frequently desired. Cruciferous plants, including Brussels sprouts, broccoli, and wasabi, have a special role in the research studies. Studies have shown that consumption of these plants reduce the risk of lung, breast, and prostate cancers. The high chemopreventive and anticancer potential of cruciferous plants results from the presence of a large amount of glucosinolates, which, under the influence of myrosinase, undergo an enzymatic transformation to biologically active isothiocyanates (ITCs). Natural isothiocyanates, such as benzyl isothiocyanate, phenethyl isothiocyanate, or the best-tested sulforaphane, possess anticancer activity at all stages of the carcinogenesis process, show antibacterial activity, and are used in organic synthesis. Methods of synthesis of sulforaphane, as well as its natural or synthetic bifunctional analogues with sulfinyl, sulfanyl, sulfonyl, phosphonate, phosphinate, phosphine oxide, carbonyl, ester, carboxamide, ether, or additional isothiocyanate functional groups, and with the unbranched alkyl chain containing 2–6 carbon atoms, are discussed in this review. The biological activity of these compounds are also reported. In the first section, glucosinolates, isothiocyanates, and mercapturic acids (their metabolites) are briefly characterized. Additionally, the most studied anticancer and antibacterial mechanisms of ITC actions are discussed. Full article

The poor water solubility of paclitaxel causes significant problems in producing cancer therapeutic formulations. Here, we aimed to solubilize paclitaxel using biocompatible cyclic carbohydrates. Generally recognized as safe, labeled β-cyclodextrin (β-CD), a cyclic α-1,4-glucan consisting of seven glucoses, was prepared, and bio-sourced cyclosophoraoses (CyS), which are unbranched cyclic β-1,2-glucans with 17–23 glucose units, were purified using various chromatographic methods from Rhizobium leguminosarum cultural broth. For effective targeting, CyS and β-CD were modified with a biotinyl moiety in a reaction of mono-6-amino CyS and mono-6-amino-β-CD with N-hydroxysuccinimide ester of biotinamidohexanoic acid. Interestingly, the aqueous solubility of paclitaxel was enhanced 10.3- and 3.7-fold in the presence of biotinyl CyS and biotinyl β-CD, respectively. These findings suggest that biotin-appended cyclooligosaccharides can be applied to improve the delivery of paclitaxel. Full article

Chiral N-protected α-amino aryl-ketones are one of the useful precursors used in the synthesis of various biologically active compounds and can be constructed via Friedel–Crafts acylation of N-protected α-amino acids. One of the drawbacks of this reaction is the utilization of toxic, corrosive and moisture-sensitive acylating reagents. In peptide construction via amide bond formation, N-hydroxysuccinimide ester (OSu), which has high storage stability, can react rapidly with amino components and produces fewer side reactions, including racemization. This study reports the first synthesis and utilization of N-trifluoroacetyl (TFA)-protected α-amino acid-OSu as a potential acyl donor for Friedel–Crafts acylation into various arenes. The TFA-protected isoleucine derivative and its diastereomer TFA-protected allo-isoleucine derivative were investigated to check the retention of α-proton chirality in the Friedel–Crafts reaction. Further utilization of OSu in other branched-chain and unbranched-chain amino acids results in an adequate yield of TFA-protected α-amino aryl-ketone without loss of optical purity. Full article

Phosphonate reagents were developed for the two-carbon homologation of aldehydes or ketones to unbranched- or methyl-branched α,β-unsaturated aldehydes. The phosphonate reagents, diethyl methylformyl-2-phosphonate dimethylhydrazone and diethyl ethylformyl-2-phosphonate dimethylhydrazone, contained a protected aldehyde group instead of the usual ester group. A homologation cycle entailed condensation of the reagent with the starting aldehyde, followed by removal of the dimethylhydrazone protective group with a biphasic mixture of 1 M HCl and petroleum ether. This robust two-step process worked with a variety of aldehydes and ketones. Overall isolated yields of unsaturated aldehyde products ranged from 71% to 86% after the condensation and deprotection steps. Full article