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Carboxylic Acids, Carboxylic Acid Derivatives, and Acyl Substitution Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Analogous to the coupling of acids and alcohols, when DCC reacts with the carboxylic acid and an amine, the products are N-cyclopentylpropionamide and dicyclohexylurea. In such reactions, the intermediate formed from DCC and the acid is attacked by the amine, giving a tetrahedral intermediate that leads to the products.
Synthesis, characterization and anticancer activity of vincristine loaded folic acid-chitosan conjugated nanoparticles on NCI-H460 non-small cell lung cancer cell line
Published in Egyptian Journal of Basic and Applied Sciences, 2018
Naresh Kumar, Raj Kumar Salar, Minakshi Prasad, Koushlesh Ranjan
Folic acid on reaction with N-hydroxysuccinimide (NHS), N,N′-dicyclohexylcarbodiimide (DCC) and triethylamine resulted in the formation of dark pale yellow colored dicyclohexylurea, confirming the synthesis of N-hydroxysuccinimide-ester of folic acid. Earlier, Salar and Kumar [14] observed yellow colored dicyclohexylurea while synthesizing vincristine loaded folic acid-chitosan conjugated nanoparticles at pH 2.5. Similarly, Ji et al. [18] also observed N-hydroxysuccinimide ester of folic acid during preparation of methotrexate loaded folic acid conjugated O-carboxymethyl chitosan nanoparticles. Further, folic acid-chitosan conjugate, dissolved in acetate buffer (pH 5.6) reacted with N-hydroxysuccinimide-ester of folic acid to form folic acid-chitosan conjugate. Similarly, Wang et al. [19] synthesized folic acid-chitosan conjugate, while loading mitoxantrone into folic acid-chitosan conjugated nanoparticles. Naghibi Beidokhti et al. [20] synthesized folic acid-chitosan conjugate by reaction of N-hydroxysuccinimide ester of folic acid with chitosan.
Synthesis of ursane-derived isothiocyanates and study of their reactions with series of amines and ammonia
Published in Journal of Sulfur Chemistry, 2023
Sergey A. Popov, Zhiwen Qi, Chengzhang Wang, Elvira E. Shults
Refluxing ursolic acid acetate 1 with an excess of diphenyl phosphorazidate for 15 h in toluene afforded the nor-derivative, isocyanate 5 (yield 58% after purification). The hydrolysis of isocyanate 5 with aqueous HCl in THF (40°C, 15 h) led to amine 6 in 64% yield. N-(2-aminoethyl)-3β-acetoxyurs-12-en-28-oyl-amide 8 was prepared by reacting 3β-acetoxy-urs-12-en-28-oyl chloride with an excess of ethylenediamine in 82% yield. To obtain ursane-derived isothiocyanates, amines 3b, 6, and 8 were treated with an excess of carbon disulfide in the presence of Et3N in THF. The intermediate salts of dithiocarbamates without isolation were reacted with iodine, the reaction products were purified by chromatography to provide isothiocyanates 4a,7, and 9 in 83–85% yields. 3-O-acetyl derivative of isothiocyanate 4b was obtained by acylation of 3-hydroxy derivative 4a with excess Ac2O in the presence of Et3N at room temperature in 85% yield. Among numerous dehydrosulfurization methods, the safest and least expensive are those using iodine and hydrogen peroxide [19]. The use of iodine in THF for the dehydrosulfurization of triterpene dithiocarbamates was the method of choice. Using THF as a solvent was preferable, due to the low solubility of amines in alcohols. Treatment of dithiocarbamates in THF with hydrogen peroxide in the presence of Et3N led to the formation of a mixture of products, from which triterpene isothiocyanates were isolated in lower yields (32%–45%). The use of N,N′-dicyclohexylcarbodiimide for the decomposition of dithiocarbamate salts similar to [11] leads to the formation of hardly separable dicyclohexylurea.