Selective Oxidation of 2-Hydroxypropyl Ethers of Cellulose and Dextran: Simple and Efficient Introduction of Versatile Ketone Groups to Polysaccharides

Abstract

Oxidation of polysaccharides has been a useful approach to new materials. However, selectivity in oxidation of polysaccharide macromolecular polyols remains a significant challenge with few methods for the synthesis of ketone-substituted polysaccharides. We report here a selective, practical, and efficient process, beginning with 2-hydroxypropyl ethers of polysaccharides that are simple and economical to prepare. We demonstrate this approach herein using commercial 2-hydroxypropyl cellulose (HPC) and 2-hydroxypropyl dextran (HPD) that we prepared. We oxidize the terminal, secondary alcohols of the oligo(2hydroxypropyl) substituents with sodium hypochlorite so that the product has an oligo(2-hydroxypropyl) side chains terminated by a ketone. We demonstrate the high chemo-and regioselectivity of this oxidation by analytical methods including hydrolysis to monosaccharides and mass spectrometry of the resulting mixture. We provide an initial demonstration of the potential utility of these keto-polysaccharides by reacting Ox-HPC with primary amines to form Schiff base imines, providing proactive polymers.

Chitosan as a Canvas for Studies of Macromolecular Controls on CaCO3Biological Crystallization

“…With advances in biopolymer synthesis, however, it is now possible to prepare macromolecules with tailored compositions and structures. ,− This capability opens the way to directly testing claims of functional group activity, providing powerful insights into the mechanistic basis of biomineralization control, particularly when combined with complementary theoretical and experimental approaches.…”

“…Many examples of hydrogels are found in natural settings, including the organic matrix. The ability to modify chitosan has advanced significantly in recent years, building upon the previously successful chemoselective modification of alginates and selective oxidation of polysaccharides as components of self-healing hydrogels. ,− …”

Photo-curable, double-crosslinked, in situ-forming hydrogels based on oxidized hydroxypropyl cellulose

“…Synthesis of oxidized hydroxypropyl cellulose (Ox-HPC) HPC oxidation followed a procedure recently developed by the Edgar group (Nichols et al 2020). HPC (4.0 g, M n 100,000 g/mol, DS = 2.2, MS = 4.4, 31.2 mmol terminal secondary hydroxyl groups) was dissolved in 50 mL DI water, then NaOCl aqueous solution (50 mL, 146.6 mmol, 4.7 equiv.)…”

“…These hydrogels were prepared by combining aminecontaining polymers (like chitosan) with oxidized oligo(hydroxypropyl)-substituted polysaccharides. The key feature of these oxidized oligo(hydroxypropyl)-substituted polysaccharides is that hydroxyl groups at the termini of the hydroxypropyl side chains were chemoselectively oxidized to ketones by reaction with sodium hypochlorite (Nichols et al 2020). The resulting ketones readily react with amine-containing polymers to form imine linkages even in water, leading to formation of a hydrogel network (Chen et al 2020a).…”

Precision Cellulose from Living Cationic Polymerization of Glucose 1,2,4-Orthopivalates

“…Enzymatic methods featuring precise regio- and stereocontrol have also been employed for cellulose synthesis. − For example, Kobayashi reported an elegant cellulase-catalyzed cellulose synthesis by employing β-cellobiosyl fluoride as the substrate (Figure A) . Using engineered glycosidases, Planas and Edgar generated functionalized celluloses with defined sequence and patterns of functionality, , highlighting their potential for a wide range of advanced biotechnological applications. However, these enzyme-catalyzed pathways often suffer from reduced efficiency and/or limited scalability, as the solubility of unprotected cellulose decreases when their lengths increase.…”