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

Abstract

Plant cell walls are composed of an intricate network of polysaccharides and proteins that varies during the developmental stages of the cell. This makes it very challenging to address the functions of individual wall components in cells, especially for highly complex glycans. Fortunately, structurally defined oligosaccharides can be used as models for the glycans, to study processes such as cell wall biosynthesis, polysaccharide deposition, protein-carbohydrate interactions, and cell-cell adhesion. Synthetic chemists have focused on preparing such model compounds, as they can be produced in good quantities and with high purity. This Review contains an overview of those plant and algal polysaccharides that have been elucidated to date. The majority of the content is devoted to detailed summaries of the chemical syntheses of oligosaccharide fragments of cellulose, hemicellulose, pectin, and arabinogalactans, as well as glycans unique to algae. Representative synthetic routes within each class are discussed in detail, and the progress in carbohydrate chemistry over recent decades is highlighted.

Glycosylation on Unprotected or Partially Protected Acceptors

“…Nevertheless, because of the biological significance of oligosaccharides, the development of facile, cheaper, and more efficient methods is the main goal in the synthesis of oligosaccharides …”

“…Nevertheless, because of the biological significance of oligosaccharides, [53] the development of facile, cheaper, and more efficient methods is the main goal in the synthesis of oligosaccharides. [54] Differentiation of hydroxyl groups in carbohydrates is the crux of oligosaccharides synthesis. [55] Masking of hydroxyl groups suppresses glycosylation at undesired positions on carbohydrates, but additional steps are required to install and remove the protecting groups.…”

Towards a Synthetic Strategy for the Ten Canonical Carrageenan Oligosaccharides – Synthesis of a Protected γ‐Carrageenan Tetrasaccharide

“…Therefore, synthetic chemists have devoted attention to developing efficient strategies for the chemical synthesis of such oligosaccharide fragments . However, as outlined by a recent review summarizing all plant and algal cell wall oligosaccharides synthesized to date, there are relatively few examples of synthetic fragments representative of marine polysaccharides. Therefore, we are interested in the synthesis of carrageenans, which are sulfated polysaccharides found in red algae seaweed .…”

Synthesis of Two Tetrasaccharide Pentenyl Glycosides Related to the Pectic Rhamnogalacturonan I Polysaccharide

“…The most frequent form of arabinogalactan side chains is arabinogalactan I, which is a β-(1→4)-galactan with arabinan branches [ 8 , 9 ]. To the best of our knowledge, except for the synthesis of tri- and tetrasaccharide building blocks containing a single galactose unit as a side chain by Vogel and co-workers [ 10 , 11 ], branched RG-I fragments have not previously been addressed by chemical synthesis [ 12 ]. These structures are of great interest because they are useful for the study of pectin and the enzymes involved in both the biosynthesis and degradation of RG-I [ 1 , 2 , 7 , 13 , 14 ].…”