Abstract
The cellobiose-derived dimer 18, tetramer 48, and octamer 49 have been prepared. Acetolytic debenzylation transformed the dimer 15, obtained from the partially benzylated, dialkynylated cellobiose 2 (Scheme 1), into 16 that was deacetylated to 18 (Scheme 2), but the analogous debenzylation of the tetramer 14 proved unsatisfactory. We, therefore, avoided benzyl groups and prepared the cellobiose-derived monomer 32 by glycosidation of 27 with the crystalline trichloroacetimidates 30 or 31 (Scheme 3). The acceptor 27 was synthesised from 1,6-anhydroglucose in 7 steps (48% overall yield), and the trichloroacetimidates 30 and 31 were obtained in good overall yields from the alkynylated glucopyranoses 29 (Scheme 3). The structure of the anomeric trichloroacetimidates 30 and 31 was determined by single crystal X-ray analysis. The alkyne 34, orthogonally C-protected by SiMe3 and GeMe3 groups, was transformed by a binomial strategy into the dimer 37, the tetramer 41, and the octamer 47 (Scheme 4). The unprotected mono- and oligomers 1, 18, 48, and 49 are soluble in H2O, MeOH, and DMSO. Their 1H-NMR specta ((D6)DMSO (1, 18, 48, 49), CD3OD (1, 18, 48), D2O (49)) show no signs of association.
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