Abstract
Methyl amyloses have been prepared under various conditions and studied as model compounds for the determination of the substitution pattern in the polymer chain. After permethylation with iodomethane- d 3 the glucosidic linkages were statistically cleaved by partial methanolysis or reductive cleavage. The distribution of substituents in the dimer-, trimer-, and tetramer fraction was determined by FAB-MS and MALDI-TOF-MS and compared with that calculated from the monomer composition. While a homogeneous methylation in water gave the expected random distribution, a reaction in Me 2SO solution with sodium hydroxide and iodomethane yielded a methyl amylose with a surprising bimodal substitution pattern. A third example indicates a ds gradient in the sample as a result of topochemical reaction control.
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