One-pot synthesis of branched oligosaccharides by use of galacto- and mannopyranosyl thioglycoside diols as key glycosylating agents

Abstract

We describe in this paper the efficient four-component one-pot synthesis of three fully protected oligosaccharides 22, 36, and 50 with di-branched structures by employing D-galacto- and mannopyranosyl thioglycoside diols as central glycosylating agents. After global deprotection, they were converted respectively into the 3-aminopropyl linker-containing free oligosaccharide fragments 14, 24, and 38 structurally related to cell wall oligosaccharides from Atractylodes lancea DC, the marine fungus Lineolata rhizophorae and pathogenic Mycobacterium tuberculosis. The 3-aminopropyl linker at the anomeric carbon can enable conjugation of these synthetic oligomers to a suitable protein carrier.

Chemical Synthesis of Oligosaccharides Related to the Cell Walls of Plants and Algae

“…For the most part, arabinogalactans with a β-(1→6)galactan backbone have been synthesized (Table 19), but two groups reported the synthesis of some fragments containing a β-(1→3)-galactan backbone, which is mostly found in arabinogalactan proteins (AGPs, Table 18). 184,185 Timmers et al 188 Du et al 189 Ning et al Timmers et al 188 Csávás et al 191 Ning et al Fekete et al 192 Liang et al 193 Bartetzko 196 The first synthesis of a tetrameric arabinogalactan with a β-(1→6)-linked backbone was achieved in 1998 by van Boom and co-workers, based on 1,2-anhydrosugar building blocks, as shown in Scheme 114 42. 188 The group synthesized three different tetrasaccharide analogues, differing in the position of the arabinofuranosyl side chain, which was linked either to the 2-, 2'-or 2''-position of the trisaccharide backbone.…”

One‐Pot Methods for the Protection and Assembly of Sugars

“…The joint applications of the regioselective and chemoselective, or preactivation‐based glycosylations in a one‐pot setting have, at a minimum, delivered complex oligomeric building blocks that are used further in stepwise glycosylations 54,58,80b,82. Several interesting targets have been completely assembled using these technique combinations, including the dibranched heptasaccharide 80 (Scheme ),83 a sialyl Lewis X hexasaccharide,84 a core 2 class glycosyl amino acid,85 branched oligoarabinoses,57b a galactomannan,86 and tigogenin saponins 56c. The remarkable preparation of compound 80 benefitted from the leaving group orthogonalities between two glucosyl halides and four thioglycosides.…”

Role of Fluoride in Accelerating the Reactions of Dialkylstannylene Acetals

“…Dialkylstannylene acetals are intermediates that are commonly employed to achieve regioselective monofunctionalization of diols or polyols, particularly carbohydrates. − The dialkylstannylene acetal intermediates react with a wide variety of electrophiles, and reactions proceed at higher rates and under milder conditions than with the parent diols. The principal advantage of these reactions, which include acylation, sulfonylation, alkylation, oxidation, and others, is that monosubstitution is obtained, often with high regioselectivity. − Although these reactions have been known since the 1970s, , their great utility, as well as debate about their mechanisms and the causes of the regioselectivity, has sparked continuing interest. − Over the past few years, conditions for some of these reactions have been developed that are catalytic in the organotin reagents. − Improved understanding of the mechanisms of these reactions could lead to improved regioselectivity and more general catalytic conditions.…”