Iterative Synthesis of Inulin-Type Fructooligosaccharides Enabled by Stereoselective ß-d-Fructofuranosylation.

ABSTRACT

Inulin-type fructooligosaccharides (FOSs) constitute an abundant subgroup of fructans with important biological activities. However, the availability of individual fructooligosaccharides with an accurate structure in high purity and quality remains challenging. We herein report the first iterative synthesis of five inulin-type FOSs with degrees of polymerization ranging from 3 to 7 via highly stereoselective ß-(2 → 1)-d-fructofuranosylation on a gram scale. Central to the synthesis is the decisive use of the 1-O-TIPS-6-O-picoloyl-protected fructofuranosyl thioglycoside donor, which assured the excellent ß-selective glycosylation by the hydrogen-bond-mediated aglycone delivery (HAD).