Chemical synthesis of 6'-alpha-maltosyl-maltotriose, a branched oligosaccharide representing the branch point of starch
1995
Motawia, M.S. | Olsen, C.E. | Enevoldsen, K. | Marcussen, J. | Moller, B.L.
Chemical synthesis of the branched pentasaccharide 6'-alpha-maltosyl-maltotriose (15) is reported, based on the use of one synthon as a glycosyl acceptor and another synthon as a glycosyl donor. The synthon used as glycosyl acceptor was phenyl 2,3,6-tri-O-benzyl-1-thio-beta-D-glucopyranoside (7) and was synthesized from D-glucose with phenyl 2,3-di-O-acetyl-4,6-O-benzylidene-1-thio-beta-D-glucopyranoside and phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1-thio-beta-D glucopyranoside as key intermediates. The synthon used as glycosyl donor was O-(2,3,4,6-tetra-O-benzyl-alpha-D-gluco-pranosyl)-(1 leads to 4)-O-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl) -(1 leads to 6)-O-[(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-(1 leads to 4)]-2,3-di-O-benzyl-alpha-beta-D-glucopyranosyl trichloroacetimidate (12) and was synthesized from phenyl O-(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-(1 leads to 4)-O-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl)-(1 leads to 6)-O-[(2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl) (1 leads to 4)]-2,3,di-O-acetyl-1-thio-beta-D-glucopyranoside with O-(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-(1 leads to 4)-O-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl)(1 leads to 6)-O-[(2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl)-(1 leads to 4)]2,3-di-O-benzyl-D-glucopyranose as an intermediate. Condensation of compounds 7 and 12 followed by removal of the phenylthio group and debenzylation provided the branched pentasaccharide 15. Alternatively, the branched pentasaccharide was produced from amylopectin consecutive alpha- and beta-amylase treatments and purified by chromatography. The identity of the products obtained by chemical synthesis and enzymatic hydrolysis is documented by 1H and 13C NMR spectra.
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