| The synthesis, structure, and solution behavior of cellulose and hyaluronan oligomers was studied by various techniques. A homologous series of cellulose oligomers from two to eight repeating subunits have been isolated and size-fractionated from the hydrolysis products of microcrystalline cellulose. Chemical modification of cellotriose (2.1), cellotetraose (2.2), cellopentaose (2.3), and cellohexaose (2.4) to the corresponding β-methyl glycosides 2.13-2.16 proceeded in three steps in overall yields of 16–46%. The complete 1H and 13C chemical shift assignments of each peracetylated and deprotected oligomer were obtained through a combination of DQF-COSY, HMQC, HMBC, and HMQC-TOCSY experiments.; The solution dynamics of an anomerically pure series of cellulose oligomers, β-methyl cellobiose (3.1) through β-methyl cellopentaose ( 3.4), were then studied by 13C NMR relaxation techniques and compared to molecular dynamics (MD) simulations of 3.1 through β-methyl cellooctaose. The NMR experiments utilized two-dimensional proton-detected 13C T1 and heteronuclear NOE pulse sequences, and the relaxation data were subsequently fit to the model-free model of Lipari and Szabo using a least-squares fitting algorithm. Striking and somewhat surprising is the experimentally observed increase in S2 from 3.1 to 3.4. Our analysis of MD simulations indicates that, given a constant degree of mobility about each individual glycosidic linkage, increasing the number of linkages should decrease the order parameter. Thus, one would expect the order parameter to decrease with oligomer size. That the opposite trend is observed indicates that each glycosidic linkage becomes much more rigid as the oligosaccharide increases in length. The effects of various denaturants on cellulose oligomer mobility were also studied.; In an effort to synthesize hyaluronan fragments, the SmI2 promoted deprotection of N-arylsulfonyl glucosamines was undertaken. The removal of the N-arylsulfonyl group proceeds in good yield (43–85%) and without disruption of the glycoside backbone or loss of other aromatic protecting groups.; To better understand the interaction of water with hyaluronan, two uronic acids, β-methyl glucuronic acid and β-methyl galacturonic acid, were prepared, and their hydroxyl protons were studied using low temperature NMR. These results were compared to calculations of proton exchange in uronic acids. Calculations suggest that OH4 in glucuronic acid should exchange with solvent, whereas in galacturonic acid it should not. The NMR observations confirm the calculated predictions. |
