Synthesis of β-d-(1→4)-Substituted Trehalose Oligosaccharides

Enzymatic Synthesis and Structural Characterization of Novel Trehalose-Based Oligosaccharides

Trehalose, α-d-glucopyranosyl-(1↔1)-α-d-glucopyranoside, is a disaccharide with multiple effects on the human body. Synthesis of new trehalose derivatives was investigated through transgalactosylation reactions using β-galactosidase from four different species. β-galactosidases from Bacillus circulans (B. circulans) and Aspergillus oryzae (A. oryzae) were observed to be the best biocatalysts, using lactose as the donor and trehalose as the acceptor. Galactosyl derivatives of trehalose were characterized using nuclear magnetic resonance spectroscopy. Trisaccharides were the most abundant oligosaccharides obtained followed by the tetrasaccharide fraction (19.5% vs 8.2% carbohydrates). Interestingly, the pentasaccharide [β-Galp-(1→4)]³-trehalose was characterized for the first time. Greater oligosaccharide production was observed using β-galactosidase from B. circulans than that obtained from A. oryzae, where the main structures were based on galactose monomers linked by β-(1→6) and β-(1→4) bonds with trehalose in the ending. These results indicate the feasibility of commercially available β-galactosidases for the synthesis of trehalose-derived oligosaccharides, which might have functional properties, excluding the adverse effects of the single trehalose.

Pivalates in the selective protection and activation of maltose for the synthesis of sulfated 3-deoxy-maltosyl-(1-->4)-alpha, alpha-trehalose

Pivaloylation of maltose gave, in satisfactory yield, 1,2,6,2',3',4',6'-hepta-O-pivaloyl-beta-maltose which was converted to the 3-deoxygenated analogue in a Barton-McCombie reaction. This compound was used directly in a trimethylsilyl triflate-mediated glycosylation reaction with 2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-D-glucopyranoside to give the corresponding maltosyl-(1-->4)-alpha, alpha-trehalose derivative. After deprotection, the monodeoxygenated tetrasaccharide was sulfated; in the reaction product, one compound fully sulfated at the outer pyranose rings predominated.