Fragmentation Pathways of Lithiated Hexose Monosaccharides

Area of Science:

• Carbohydrate Chemistry
• Mass Spectrometry
• Computational Chemistry

Background:

• Understanding carbohydrate structure is crucial in biochemistry and medicine.
• Mass spectrometry is a powerful tool for analyzing complex molecules like sugars.
• Isomeric sugars present analytical challenges due to similar masses and structures.

Purpose of the Study:

• To characterize the primary fragmentation reactions of lithiated D-hexose isomers (glucose, galactose, mannose).
• To elucidate the influence of sugar structure and anomeric configuration on fragmentation pathways.
• To compare experimental findings with theoretical predictions.

Main Methods:

• Tandem mass spectrometry (MS/MS) was employed.
• Regiospecific labeling was used to track atom movement.
• Computational theory was applied to model reaction energetics.

Main Results:

• Lithiated glucose, galactose, and mannose share common cross-ring cleavage pathways (0,2A1 and 0,3A1).
• Energetics and rate-determining steps vary significantly with sugar isomer and anomeric configuration.
• Distinct water loss pathways produce different B1 ions (e.g., ketone vs. anhydro structures) based on precursor structure and conformer.

Conclusions:

• Fragmentation patterns are sensitive to subtle structural differences in lithiated hexoses.
• Anomeric configuration and stereochemistry at C2 dictate specific reaction mechanisms, particularly water loss.
• The study provides detailed insights into the mass spectrometry fragmentation of isomeric carbohydrates.