Largest Synthetic Polysaccharide Assembled
30 Apr 2020 by Sarah Lawton
Chemists at the Max Planck Institute of Colloids and Interfaces (Potsdam, Germany) have set a milestone by preparing the two largest carbohydrates ever assembled. Using an Automated Glycan Assembly (AGA) instrument originally developed at the institute, they prepared a linear 100-mer and achieved the completion of a 151-mer multi-branched polysaccharide. Access to defined polysaccharides gives insight into how these ubiquitous biopolymers serve their roles as materials.
Carbohydrates are the most dominant biopolymers on earth. Polysaccharides, such as cellulose, are the building materials for plants and the chitin shells that protect some animals. Even though Nature produces 100s of millions of tons of cellulose and chitin each year, access to completely defined polysaccharides has proven extremely difficult.
In recent years, synthetic chemists have attempted to prepare long polysaccharides from single building blocks. A group from Peking University, led by Prof Xin-Shan Ye, set a new record in 2017 when a tremendous group effort produced a branched 92-mer.
Linear 100-mer polysaccharide within 188 hours
Now, two chemists, postdoctoral fellow Dr Abragam Joseph and PhD student, Alonso Pardo-Vargas, in the team led by Peter H. Seeberger, Director at the Max Planck Institute of Colloids and Interfaces (Potsdam, Germany), used an automated synthesis instrument to prepare a linear 100-mer polysaccharide from one building block and within 188 hours.
The team illustrated that polysaccharide chains such as 30-mers and 31-mers, prepared by the automated AGA method, can in turn be combined to form polysaccharides of unprecedented size and complexity as illustrated by the 31+30+30+30+30 coupling to form a multiply branched 151-mer.
Defined polysaccharides open up insights to all aspects of carbohydrates
Access to complex polysaccharides is the basis for investigations into fundamental structural processes such as previously difficult to understand carbohydrate folding. The ability to quickly and reliably prepare such defined molecules gives scientists the tools to study all aspects of carbohydrates that have so far been impossible.
“Even two years ago, I would not have dared to dream that it would be possible to prepare 100- and even 150-mer polysaccharides. Systematic improvements in our chemical methods, combined with better automated coupling protocols, now provide us with extremely interesting tools to better understand carbohydrates,” said Seeberger.
The original paper is currently in press with the Journal of American Chemistry: Joseph, A.; Pardo-Vargas, A.; Seeberger, P.H. Total Synthesis of Polysaccharides by Automated Glycan Assembly, J. Am. Chem. Soc., 2020, 142, in press
