Enhancing glycan stability via site-selective fluorination: modulating substrate orientation by molecular design.

Area of Science:

• Carbohydrate Chemistry
• Medicinal Chemistry
• Enzymology

Background:

• Maltodextrins are crucial in bacterial imaging and medicinal chemistry.
• Carbohydrates possess inherent hydrolytic vulnerabilities.
• C(sp3)-F bioisosteres are increasingly popular in drug design.

Purpose of the Study:

• To investigate the impact of single-site fluorine substitution on oligosaccharide hydrolytic stability.
• To explore the effect of molecular editing on maltotetraose stability against enzymatic degradation.
• To understand how fluorine influences the interaction of oligosaccharides with enzymes and biological systems.

Main Methods:

• Convergent alpha-selective synthesis of selectively modified oligosaccharides.
• Incubation experiments with purified alpha-amylase and alpha-glucosidase.
• Stability assessments in human and murine blood serum.
• Molecular docking studies and co-crystal structure analysis of enzyme-substrate interactions.

Main Results:

• Single site OH to F substitution at maltotetraose termini significantly improved hydrolytic stability (approx. 1 order of magnitude) against alpha-amylase and alpha-glucosidase.
• Modification at the monosaccharide furthest from cleavage sites yielded the greatest stability enhancement.
• Docking studies showed C2-fluorination at the reducing end inverts substrate binding orientation in alpha-amylase.
• Co-crystal structure revealed maltose units bound at the human alpha-amylase active site.

Conclusions:

• Single-point fluorine mutations offer a strategy to enhance the hydrolytic stability of oligosaccharides.
• Fluorine substitution can modulate enzyme-substrate interactions, offering potential for drug design and imaging applications.
• This work bridges the gap between the information content of carbohydrates and their stability limitations.