Solution- and solid-phase oligosaccharide synthesis using glucosyl iodides: a comparative study

Glycosyl iodide donors have been used in both solid- and solution-phase syntheses yielding alpha-(1 --> 6)-linked glucosyl oligomers in highly efficient protocols. While the solid-phase strategy offers advantages in terms of case of purification, it requires a total of 7.5 equiv of donor and approximately 12 h to complete the incorporation of one monosaccharide unit. In contrast, solution-phase methods require only 2.5 equiv of donor and 2-3 h reaction time per glycosylation. Moreover, since the reactions are virtually quantitative (>90%) column chromatography of the material is facile. The overall advantages of solution-phase ligosaccharide synthesis were further illustrated in the convergent synthesis of a hexamer (methoxycarbonylmethyl 6-O-acety-1,2,3,4-tri-O-benzyl-7-D-glucopyranosyl-(1 --> 6)-tetrakis-(2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl-(1 --> 6))-2,3,4-tri-O-benzyl-1-thioa-D-glucopyranoside) that was constructed from dimer donor iodides in a two-plus-two and a two-plus-four fashion. (C) 2002 Elsevier Science Ltd. All rights reserved.