Synthesis of 6-Branched Cyclo-(1→3)-glucohexaose and Glucooctaose

Abstract

The cyclization precursors nonasaccharide 3 and dodecasaccharide 8 were obtained, respectively, from the corresponding 4-methoxyphenyl glycosides 1 and 6 via oxidative cleavage of 1-OMp followed by selective 1-O-trichloroacetimidate formation. TMSOTf-promoted cycloglycosylation of 3 and 8 went smoothly giving a-linked cyclized nonasaccharide 4 and dodecasaccharide 9. Finally, deacylation of 4 and 9 furnished the target cycloglucans 5 and 10 consisting of alternate b-and a-(1→3)-linked cycloglucohexaose backbone bearing three b-(1→6)-linked glucose side chains and cycloglucooctaose backbone bearing four b-(1→6)-linked glucose side chains, respectively. The side chains were attached at the glucose residue of the backbone with a-linkage.