Synthesis, control of substitution pattern and phase transitions of 2,3-di-O-methylcellulose

Kern, H.; Choi, SooWhan; Wenz, Gerhard; Heinrich, Jürgen; Ehrhardt, Lutz; Mischnick, Petra; Garidel, Patrick; Blume, Alfred

doi:10.1016/s0008-6215(00)00024-0

Cited by 56 publications

(55 citation statements)

References 28 publications

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“…Resolution of the signals increases with increasing uniformity of these ethers and minor signals could be assigned and correlated with special structural features. [17] Starch derivatives with their amylose/amylopectin heterogeneity and usually very low DS values have been far less the objective of NMR studies. In contrast, cyclodextrins with their defined core structures and often regioselective substitution patterns are usually analyzed by NMR spectroscopy as it is common in structure elucidation and synthesis control of organic compounds.…”

Section: Nmr Spectroscopymentioning

confidence: 99%

Structure analysis of 1,4-glucan derivatives

Mischnick

Heinrich

Gohdes

et al. 2000

Macromol. Chem. Phys.

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Cellulose, starch and cyclodextrin ethers and esters are produced for many fields of application as for example oil recovery, building and ceramic materials, textile and paper industry, food, cosmetics, and pharmaceuticals. For further development of new types of derivatives and also for a better understanding of their properties a detailed analysis of the usually complex mixtures is required. By complete degradation, separation and quantification of appropriate monomer derivatives the regioselectivity in the glucose unit can be determined. For the determination of the substitution pattern in the polymer chain partial random degradation, oligomer analysis by mass spectrometry, and subsequent statistical evaluation can be applied. The composition of products obtained by enzymatic degradation also reflects the pattern in the polymer chain. In addition a possible heterogeneity of the material must be taken into consideration, since any degradation averages the structural information.

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Section: Nmr Spectroscopymentioning

confidence: 99%

Structure analysis of 1,4-glucan derivatives

Mischnick

Heinrich

Gohdes

et al. 2000

Macromol. Chem. Phys.

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“…Homogeneous reaction yielding tosylated cellulose was carried out by allowing cellulose to react with tosyl chloride in [amim] Kern et al 2000). Subsequent S N reactions on tosylated cellulose have some limitations if reactions are carried out on tosyl cellulose with DS value of greater than 1.…”

Section: Tosylationmentioning

confidence: 99%

Tosylation and acylation of cellulose in 1-allyl-3-methylimidazolium chloride

et al. 2008

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Tosylation and acylation of cellulose were performed under mild reaction conditions using imidazolium based ionic liquids (ILs) as solvents. The non-degradative nature, lower viscosity, as well as higher solubility of cellulose in [amim]Cl encouraged us to carry out the reactions in this media. The reactions described here were optimised for this particular solvent in order to obtain different cellulose derivatives with high yields, homogeneity and degree of substitution (DS). Two reagents employed for the in situ activation of carboxylic acids were N,N 0 -carbonyldiimidazole (CDI) and 1-ethyl-3-(3 0 -dimethylaminopropyl)carbodiimide hydrochloride (EDCI). Final products were characterised by solution and solid-state NMR techniques.

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“…The trityl moiety has been reported to possess the highest regioselectivity among the known blockers of the primary C6 -hydroxyl functions of polysaccharides and should not attach to the secondary hydroxyl groups in position C2 and C3. 39,40,48 Alkylation was effected by reaction of 6-Otriphenylmethyl-amylose with alkyl iodides using Ktert-butoxide as base 41,42 ( Figure 1). The reaction became less effective with increasing alkyl chain length, and the procedure had to be repeated several times to obtain higher degrees of substitution.…”

Section: Synthesis Of 23-di-o-alkylated Amylosesmentioning

confidence: 99%

“…Trityl removal from the polymeric materials was not efficient, as is known for polyglucans. 48 Due to the varying solubility of the products, three strategies for detritylation were employed ( Figure 1): (A) Aqueous HCL in methanol, 40 for hydrophilic amylose derivatives; (B) trifluoroacetic acid in n-butanol, 44 for alkyl amyloses of intermediate hydrophobicity; (C) gaseous HCL in chloroform 45 for highly hydrophobic amyloses. Usually detritylation had to be repeated several times to ensure complete removal of trityl groups, as monitored by uv absorption.…”

Section: Synthesis Of 23-di-o-alkylated Amylosesmentioning

confidence: 99%

“…Recent synthetic advances, including the use of the more easily removable p-methoxytrityl group, 53,54 have allowed synthesis and determination of substitution patterns of various polyglucans. 48,55,56 Such strategies should eventually give access to tailor-made polysaccharide compounds. Alkylated amyloses should be useful polymeric materials, such as plasticizers, or emulsifiers, were controlled hydrophobicity and simultaneous interaction with nonpolar and polar substances is required.…”

Section: Flexible Helical Conformation Of Amylosementioning

confidence: 99%

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Synthesis and characterization of 2,3‐di‐O‐alkylated amyloses: Hydrophobic substitution destabilizes helical conformation

Breitinger

2003

Biopolymers

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Amylose was selectively alkylated in the 2,3-O position of each anhydroglucose unit after trityl protection of the 6-OH groups. Alkyl iodides of varying chain length (C(2), C(5), C(8)) were coupled to amylose, and degrees of substitution (DSs) were varied between 0.3 and 1.8, as assessed by NMR analysis. Increasing amounts of methyl groups per anhydroglucose unit increased solubility in nonaqueous media, while at the same time reducing the ability of modified amylose to form a complex with iodine. The tendency to form inclusion complexes with the surfactant N-dodecyl pyridinium bromide decreased in the order beta-cyclodextrin >> amylose approximately solubilized starch, indicating that the frozen macrocycle of beta-cyclodextrin was the most efficient inclusion host. Introduction of the bulky trityl group abolished the helical amylose conformation, which is not readily reassumed in the presence of hydrophobic substitution of the C2 and C3 positions. These results indicated that a polar outer surface is necessary but not sufficient for the formation of a stable amylose helix.

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Synthesis, control of substitution pattern and phase transitions of 2,3-di-O-methylcellulose

Cited by 56 publications

References 28 publications

Structure analysis of 1,4-glucan derivatives

Structure analysis of 1,4-glucan derivatives

Tosylation and acylation of cellulose in 1-allyl-3-methylimidazolium chloride

Synthesis and characterization of 2,3‐di‐O‐alkylated amyloses: Hydrophobic substitution destabilizes helical conformation

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