6214-01-3Relevant academic research and scientific papers
Formation and characterisation of a physical chitin gel
Vachoud, Laurent,Zydowicz, Nathalie,Domard, Alain
, p. 169 - 177 (1997)
The formation of N-acetyl chitosan gels in anacetic acid-water-propanediol solution was studied. Side reactions arising from the esterification of 1,2-propanediol by acetic anhydride, and hydrolysis of acetic anhydride were studied, as well as their possible role on the gel formation. The gels were studied by FTIR and 1H NMR spectroscopy. Independently of the initial acetylation degree of chitosan, a minimal acetylation degree is required for gelation (80%). The final acetylation degree of the gels increases with the molar ratio acetic anhydride/amine, but does not reach 100%. An increase in temperature favours the molecular mobility, inter- and intra-molecular hydrogen bondings and hydrophobic interactions, responsible for gelation which appears to depend on two parameters: a critical acetylation degree and a critical molecular weight allowing the aggregation of the polymer chains. The nature of the solvent used to avoid chitosan side reactions during gelation (ethanol or propanediol) does not influence the chemical structure of the gel but only the kinetics of gelation.
COMPOUNDS AND COMPOSITIONS FOR OCULAR DELIVERY
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Page/Page column 108; 211, (2020/05/12)
The present invention provides new prodrags of Sunitinib, Brinzolamide, and Dorzolamide and compositions to treat medical disorders, for example glaucoma, a disorder or abnormality related to an increase in intraocular pressure (TOP), a disorder requiring neuroprotection, age-related macular degeneration, or diabetic retinopathy.
Homogeneous and silica-supported zinc complexes for the synthesis of propylene carbonate from propane-1,2-diol and carbon dioxide
Comerford, James W.,Hart, Sam J.,North, Michael,Whitwood, Adrian C.
, p. 4824 - 4831 (2016/07/11)
Three organozinc complexes have been synthesised and found to catalyse the carbonylation of propylene glycol with carbon dioxide to form propylene carbonate. A similar tethered organozinc complex was supported onto high loading aminopropyl functionalised hexagonal mesoporous silica and was also found to be catalytically active.
H-bonding activation in highly regioselective acetylation of diols
Zhou, Yixuan,Rahm, Martin,Wu, Bin,Zhang, Xiaoling,Ren, Bo,Dong, Hai
, p. 11618 - 11622 (2013/12/04)
H-bonding activation in the regioselective acetylation of vicinal and 1,3-diols is presented. Herein, the acetylation of the hydroxyl group with acetic anhydride can be activated by the formation of H-bonds between the hydroxyl group and anions. The reaction exhibits high regioselectivity when a catalytic amount of tetrabutylammonium acetate is employed. Mechanistic studies indicated that acetate anion forms dual H-bonding complexes with the diol, which facilitates the subsequent regioselective monoacetylation.
Regio- and stereoselective transacylation of polyhydric alcohols using pronase in organic solvents
Bhattacharya, A,Ali, E
, p. 898 - 899 (2007/10/02)
Pronase a mixture of proteases from Streptomyces griseus has been found to be a good catalyst for transacylation in organic solvents.With equimolar concentrations of p-nitrophenyl acetate as acyl donor in pyridine, aliphatic diols give predominantly the monoacetates.Glucose and isomeric hexoses give the 6-O-acetates in good yield. 6-Deoxy-sugars however, yield mixtures of acetates indicating that regioselectivity among the secondary hydroxyl groups are poor.Racemic trans-1,2-cyclohexanediol affords the (1R, 2R)-monoacetate in 44percent yield with greater than 90percent enantiomer ic purity. cis-1,2-cyclohexanediol and cis-1,2-cyclohexanedimethanol also give optically active monoacetates.
OXIDATION OF CYCLIC ACETALS BY HYDROGEN PEROXIDE
Nazarov, M. N.,Kuramshin, E. M.,Zlotskii, S. S.,Rakhmankulov, D. L.
, p. 1258 - 1260 (2007/10/02)
The hydroxylation of cyclic acetals by hydrogen peroxide leads to the formation of the monoesters of glycols, which are the principal reaction products.During the hydroxylation of 4-substituted 1,3-dioxacyclanes two isomeric monoesters are formed, and the ester with a primary acylated hydroxyl group predominates.
Formation of Glycol Monoacetates in the Oxidation of Olefins Catalyzed by Metal Nitro Complexes: Mono- vs. Bimetallic System
Mares, Frank,Diamond, Steven E.,Regina, Francis J.,Solar, Jeffrey P.
, p. 3545 - 3552 (2007/10/02)
The oxidation of terminal olefins by bis(acetonitrile)chloronitropalladium(II) (1) in acetic acid leads to a mixture of glycol monoacetate isomers as the main products.Various amounts of ketones and unsaturated acetates are also formed.The rate of formation and the yield of glycol monoacetate decrease with increasing chain length.Cyclic olefins yield no glycol monoacetates.Replacement of acetic acid by stronger or sterically hindered carboxylic acids completely eliminates the formation of glycol monocarboxylates.Introduction of oxygen converts this stoichiometric reaction into a catalytic system.Our studies, including those carried out with complex 1 labeled with 18O in the nitro ligand, suggest that the glycol monoacetates and most of the ketones are the product of oxygen atom transfer from the nitro group, while the unsaturated acetates are the result of a Wacker-type reaction.In the glycol monoacetate, the 18O label is found exclusively in the acetate group.A mechanism which is in agreement with the above observations as well as a comparison of the above reaction with the oxidation of olefins by nitrate ions in the presence of palladium(II) salts is offered.The formation of glycol monoacetates in the monometallic system represented by complex 1 is to be compared with the results obtained in the bimetallic systems consisting of a combination of py(TPP)CoNO2 and either (CH3CN)2PdCl2 or Pd(OAc)2.In the latter systems, ketones or vinyl acetates are found as the predominant products.This fact underlines the difference between the mono- and bimetallic systems and strongly argues against alternative mechanisms involving nitro group transfer from cobalt to palladium before the olefin oxidation takes place.Additional evidence underlining the difference between these two systems is presented.
