Oligosaccharide analogues of polysaccharides part 20 - MMR analysis of templated cellodextrins possessing two parallel chains: A mimic for cellulose I?

Naphthalene-1-ethanol and naphthalene-1,8-diethanol carrying one or two gly cosidicalty bonded cellodextrin chains, T-x and T-x-x, resp. (x = 1-4, 8) w ere analyzed by NMR spectroscopy. For solutions in (D-6)DMSO and (D-5)pyrid ine, analysis was based on a comparison of chemical shifts, coupling consta nts, temperature dependence of OH signals, and ROESY spectra of the singly and doubly substituted T-x and T-x-x. The characteristic strong intrachain inter-residue O(3)-H ... O(5') H-band of celluloses was detected in the sin gly and doubly substituted naphthalenes. Also detected was a weakly persist ent flip-flop H-bond between HO(2') and HO(6). Weak interchain interactions were, however, observed only for the units closest to the link of T-x-x in (D-6)DMSO and for parallel units of T-1-1 and T-3-3 in (D-5)pyridine. Inte rchain interactions in T-x-x are stronger in (D-5)pyridine than in (D-6)DMS O and decrease with increasing distance from the link. The solid state CP/M AS C-13-NMR spectra of T-x-x were compared with those of T-x and of cellulo ses. The spectrum of T-8 and, surprisingly, also of T-8-8 strongly resemble s that of cellulose II and not that of cellulose I-beta, evidencing that a flexible template possessing parallel cellodextrin chains does not impose s ufficient constraints on the structure of supramolecular assemblies to mimi c cellulose I-beta but leads to a valuable mimic of cellulose II.