Trialkylsilyl derivatives of cyclomaltoheptaose, cellulose, and amylose: rearrangement during methylation analysis

Mischnick, Petra; Lange, Melanie; Gohdes, Michael; Stein, A.; Petzold, Katrin

doi:10.1016/0008-6215(95)00202-5

Cited by 36 publications

(13 citation statements)

References 27 publications

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“…A similar behavior was observed by the silylation of starch with tert-butyldimethylsilyl chloride (TBDMSCl). [12] But the silylation using TDSCl shows higher regioselectivity. Therefore, only it will be discussed in this section.…”

Section: Resultsmentioning

confidence: 99%

“…tion conditions can differentiate the preferred silylation. [11,12] In the case of polymer-analogous reactions on polysaccharides, the polymer solubility, the accessibility of functional groups, and phase and conformation state of the polysaccharide play a more critical role during reaction. Additionally, the characteristic features of native starches containing the polymers amylose and amylopectin (Scheme 1) are very important.…”

Section: Introductionmentioning

confidence: 99%

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Preparative and1H NMR Investigation on Regioselective Silylation of Starch Dissolved in Dimethyl Sulfoxide

Einfeldt¹,

Petzold²,

Günther³

et al. 2001

Macromol. Biosci.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Preparative and1H NMR Investigation on Regioselective Silylation of Starch Dissolved in Dimethyl Sulfoxide

Einfeldt¹,

Petzold²,

Günther³

et al. 2001

Macromol. Biosci.

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“…For the b-linked trialkylsilyl celluloses this requirement could be fulfilled, while in the corresponding a-glucans nearly complete migration of the SiR 3 group from O-2 to O-3 occurred under the alkaline methylation conditions, and the 2-position was irreversibly methylated. [51,52] This rearrangement interferes with the analytical target, but is a valuable tool for regioselective synthesis of 2-O-methyl-a-glucans. Methylation with methyl triflate and 2,6-tert-butylpyridine occurs without silyl migration, since no active nucleophile for the intramolecular attack is formed.…”

Section: Nmr Spectroscopymentioning

confidence: 99%

“…Methanolysis can be applied prior to acid hydrolysis to hydrophobic trialkyl silyl ethers in a two-step procedure. [51] Methyl glucosides obtained from cationic starches via methanolysis are isolated on an anion exchange column (Bio-Rad, AG 1-X4, [OH -]) with water as eluent. [44] Reduction and acetylation: Free sugars obtained by hydrolysis are reduced with 0.5 M NaBD 4 in 2 M ammonia for 1 h at 60 8C.…”

Section: Experimental Partmentioning

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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“…In the case of starch, the rst example for selective methylation of free secondary OH groups in TBDMS amylose with a DS of 1.6 was described [22].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and NMR characterization of regiocontrolled starch alkyl ethers

Petzold¹,

Klemm²,

Stein³

et al. 2002

Designed Monomers and Polymers

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Selective polysaccharide functionalization is of importance in molecular and supramolecular structure design and the development of new products and properties. As a typical partially branched polysaccharide, starch (72% amylopectin) was selectively and completely alkylated in the secondary positions. Starting from 6-O-thexyldimethylsilyl starch (6-O-TDS starch) prepared regiocontrolled, an effective alkylation takes place by using methyl iodide and benzyl bromide, respectively, and sodium hydride as a base in THF solution. Under these conditions, the silyl ether linkages are stable. The subsequent desilylation proceeded with tetra-n-butylammonium uoride (TBAF) under mild conditions to form the alkyl starches without cleavage of the alkyl ether linkage. The pattern of functionalization could be analyzed by using the silyl alkyl ethers or subsequently 6-O-acetylated derivatives and multidimensional NMR techniques. In the case of the methyl ethers, the substituent distribution could be detected not only in the anhydroglucose units (AGUs), but also in the nonreducing end-groups (NEGs). As a result, the starch ethers are alkylated regiocontrolled in 2,3-di-O (AGU) and 2,3,4-tri-O (NEG) positions.

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Trialkylsilyl derivatives of cyclomaltoheptaose, cellulose, and amylose: rearrangement during methylation analysis

Cited by 36 publications

References 27 publications

Preparative and1H NMR Investigation on Regioselective Silylation of Starch Dissolved in Dimethyl Sulfoxide

Preparative and1H NMR Investigation on Regioselective Silylation of Starch Dissolved in Dimethyl Sulfoxide

Structure analysis of 1,4-glucan derivatives

Synthesis and NMR characterization of regiocontrolled starch alkyl ethers

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