Polysaccharides are the most abundant biopolymers on earth that serve various structural and modulatory functions. Pure, completely defined linear and branched polysaccharides are essential to understand carbohydrate structure and function.Polysaccharide isolation provides heterogeneous mixtures, while heroic efforts were required to complete chemical and/or enzymatic syntheses of polysaccharides as long 92-mers. Here, we show that automated glycan assembly (AGA) enables access to a 100-mer polysaccharide via a 201-step synthesis within 188 h. Convergent block coupling of 30-and 31-mer oligosaccharide fragments, prepared by AGA, yielded a multiple-branched 151-mer polymannoside. Quick access to polysaccharides provides the basis for future material science applications of carbohydrates.
A highly efficient TMSOTf-catalyzed HMDS silylation of sugars, which can easily be integrated with subsequent reactions in one-pot fashion, has been developed. Its usefulness was demonstrated by applications to streamlined regioselective one-pot protection and nonenzymatic acetylation of un-
Automated synthesis
of DNA, RNA, and peptides provides quickly
and reliably important tools for biomedical research. Automated glycan
assembly (AGA) is significantly more challenging, as highly branched
carbohydrates require strict regio- and stereocontrol during synthesis.
A new AGA synthesizer enables rapid temperature adjustment from −40
to +100 °C to control glycosylations at low temperature and accelerates
capping, protecting group removal, and glycan modifications using
elevated temperatures. Thereby, the temporary protecting group portfolio
is extended from two to four orthogonal groups that give rise to oligosaccharides
with up to four branches. In addition, sulfated glycans and unprotected
glycans can be prepared. The new design reduces the typical coupling
cycles from 100 to 60 min while expanding the range of accessible
glycans. The instrument drastically shortens and generalizes the synthesis
of carbohydrates for use in biomedical and material science.
A highly efficient CH3CN-promoted hexamethyldisilazane per-O-trimethylsilylation of amino sugars was developed. Its applications in homogenous N-functionalisation and a concise synthesis of glucosamine 6-phosphate are described.
Carbohydrates, such
as oligo- and polysaccharides, are highly abundant
biopolymers that are involved in numerous processes. The study of
their structure and functions is commonly based on a material that
is isolated from complex natural sources. However, a more precise
analysis requires pure compounds with well-defined structures that
can be obtained from chemical or enzymatic syntheses. Novel synthetic
strategies have increased the accessibility of larger monodisperse
polysaccharides, posing a challenge to the analytical methods used
for their molecular characterization. Here, we present wide mass range
ultrahigh-resolution matrix-assisted laser desorption/ionization (MALDI)
Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry
(MS) as a powerful platform for the analysis of synthetic oligo- and
polysaccharides. Synthetic carbohydrates 16-, 64-, 100-, and 151-mers
were mass analyzed and characterized by MALDI in-source decay FT-ICR
MS. Detection of fragment ions generated from glycosidic bond cleavage
(or cross-ring cleavage) provided information of the monosaccharide
content and the linkage type, allowing for the corroboration of the
carbohydrate compositions and structures.
Biologically essential carbohydrate 6-phosphates, especially trehalose 6-phosphate, can be synthesized easily in excellent overall yields in 2 steps involving minimum protecting group manipulations. We can cleave the diphenylphosphate group for further synthetic objectives.
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