Optical rotation linkages

Mutarotation (Section 25.5) The change in optical rotation observed when a pure anomer of a sugar is dissolved in water. Mutarotation is caused by the reversible opening and closing of the acetal linkage, which yields an equilibrium mixture of anomcrs. 

Freudenberg later concurred with French s results, after studying the X-ray measurements of Borchert and also his and Cramer s optical rotation data. He also proposed that the gamma dextrin consisted of eight d-glucosyl residues joined by a linkages in a cyclic structure, as in the case of the alpha and beta dextrins. 

N 142 "Conformational Analysis of Polysaccharides. Part V. The Characterization of Linkage Conformations (Chain Conformations) by Optical Rotation at a... 

Complete hydrolysis of the polyglycoses gave the starting monomer. Hydrolysis with dilute acid gave an initial rise in optical rotation which was attributed to the hydrolysis of furanosidic bonds. The positive rotations suggest the presence of o-d as well as of 0-D-glycosidic linkages. The isolation... 

The specific optical rotation of these polymers ([a]f> + 91° =b 5°) led Schuerch and coworkers 1 to suggest that they contain a minor preponderance of a-D-glucoeidic linkages. Only pyranoid forms were assumed to be present. In view of the finding of furanoid residues in other synthetic polysaccharides,15 1 2 this supposition is no longer valid. Additional experimental data, such as the results of methylation studies, must be acquired before the chemical structure of these complicated polymers can be formulated. 

Attempts to obtain chemical data to support the optical rotation evidence for the V-glycoside type of structure were unsuccessful, owing to the labile nature of the desoxysugar-base linkage.223 By infrared absorption spectra measurements, however, it was demonstrated that... 

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