Synthesis of Polyanionic Cellulose Carbamates by Homogeneous Aminolysis in an Ionic Liquid/DMF Medium

Polyanionic cellulose carbamates were synthesized by rapid and efficient homogeneous aminolysis of cellulose carbonate half-esters in an ionic liquid/DMF medium. Cellulose bis-2,3-O-(3,5-dimethylphenyl carbamate), as a model compound, reacted with different chloroformates to cellulose carbonates. These intermediates were subjected to aminolysis, for which both the reactivity of different chloroformates towards C6-OH and the reactivity/suitability of the respective carbonate half-ester in the aminolysis were comprehensively studied. Phenyl chloroformate and 4-chlorophenyl chloroformate readily reacted with C6-OH of the model cellulose derivative, while 4-nitrophenyl chloroformate did not. The intermediate 4-chlorophenyl carbonate derivative with the highest DS (1.05) was then used to evaluate different aminolysis pathways, applying three different amines (propargyl amine, β-alanine, and taurine) as reactants. The latter two zwitterionic compounds are only sparingly soluble in pure DMF as the typical reaction medium for aminolysis; therefore, several alternative procedures were suggested, carefully evaluated, and critically compared. Solubility problems with β-alanine and taurine were overcome by the binary solvent system DMF/[EMIM]OAc (1:1, v/v), which was shown to be a promising medium for rapid and efficient homogeneous aminolysis and for the preparation of the corresponding cellulose carbamate derivatives or other compounds that are not accessible by conventional isocyanate chemistry. The zwitterionic cellulose carbamate derivatives presented in this work could be promising chiral cation exchangers for HPLC enantiomer separations.

Magnetic sulfonated polysaccharides as efficient catalysts for synthesis of isoxazole-5-one derivatives possessing a substituted pyrrole ring, as anti-cancer agents

Four polysaccharides (chitosan, cellulose, starch, and pectin) were magnetized with magnetic iron oxide (Fe₃O₄) and then sulfonated (except pectin) with chlorosulfonic acid. The obtained solid acids were used as a catalyst in three-component reactions between N-substituted-2-formylpyrrole, hydroxylamine-hydrochloride, and β-keto esters for the synthesis of 4-(2-pyrrolyl) methylene-isoxazole-5-ones. The optimal catalyst system was selected and studied by IR, SEM, TEM and XRD methods. The diverse isoxazoline derivatives (obtained via a mild and simple approach) were also fully characterized by spectroscopic methods and screened for anti-cancer activities against HT-29 and MCF-7 colon and breast cancer and HEK 293 normal cells. The results revealed interesting anti-cancer activities.

Four magnetic polysaccharides containing acidic groups were used as catalysts for the synthesis of 4-(2-pyrrolyl) methylene-isoxazole-5-ones. The products showed anti-cancer activities.

Cellulose carbonates: a platform for promising biopolymer derivatives with multifunctional capabilities

Cellulose carbonates as a platform compound open new possibilities for the design of advanced materials based on the most important renewable resource cellulose. In the present feature, the chemistry of cellulose carbonates is discussed considering own research results adequately. After a short overview about methods for activation of polysaccharides for a conversion with nucleophilic compounds in particular with amines, details about various methods for the synthesis of polysaccharide carbonates are discussed. The main issue of the feature is the synthesis and aminolysis of cellulose carbonates with low, intermediate, and high degree of substitution and the evaluation of this chemistry with respect to specific challenges. Functional cellulose carbamates, obtained from cellulose phenyl carbonate by aminolysis, show the potential use of this class of celluloses. Immunoassays and zwitterionic polymers are included as representative examples regarding properties and application of the new cellulose-based products.

Synthesis of cellulose methylcarbonate in ionic liquids using dimethylcarbonate

Dialkylcarbonates are viewed as low-cost, low-toxicity reagents, finding application in many areas of green chemistry. Homogeneous alkoxycarbonylation of cellulose was accomplished by applying dialkycarbonates (dimethyl and diethyl carbonate) in the ionic liquid-electrolyte trioctylphosphonium acetate ([P8881 ][OAc])/DMSO or 1-ethyl-3-methylimidazolium acetate ([emim][OAc]). Cellulose dialkylcarbonates with a moderate degree of substitution (DS∼1) are accessible via this procedure and cellulose methylcarbonate was thoroughly characterized for its chemical and physical properties after regeneration. This included HSQC & HMBC NMR, ATR-IR, molecular weight distribution, morphology, thermal properties, and barrier properties after film formation.

Alginic acid: a highly efficient renewable and heterogeneous biopolymeric catalyst for one-pot synthesis of the Hantzsch 1,4-dihydropyridines

Alginic acid was found to be an efficient, environmentally benign, easily recoverable and low-cost catalyst for clean synthesis of 1,4-dihydropiridine derivatives (DHPs).

Synthesis of cellulose tricarbonates in 1-butyl-3-methylimidazolium chloride/pyridine

Cellulose phenyl tricarbonates could be synthesized by a novel and fast procedure applying 1-butyl-3-methylimidazolium chloride/pyridine as reaction medium. Even cellulose phenyl carbonates with high degree of substitution are accessible at low molar ratio very efficiently. The reagent phenyl chloroformate is inert in the mixture, which is different from the solvent N,N-dimethylacetamide/LiCl that is usually applied. The products were characterized in detail by two-dimensional NMR- and FTIR-spectroscopy, elemental analysis, and size-exclusion chromatography. This class of cellulose derivatives is a very important intermediate for the design of structures based on cellulose by nucleophilc attack on the carbonyl group.