Analysis of Synthetic Monodisperse Polysaccharides by Wide Mass Range Ultrahigh-Resolution MALDI Mass Spectrometry.

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.

Total Synthesis of Polysaccharides by Automated Glycan Assembly.

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.

Chemoselective per-O-trimethylsilylation and homogeneous N-functionalisation of amino sugars.

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.

Simple one-pot regioselective 6-O-phosphorylation of carbohydrates and trehalose desymmetrization.

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.