Unprotected Galactosamine as a Dynamic Key for a Cyclochiral Lock

Area of Science:

• Supramolecular Chemistry
• Analytical Chemistry
• Mass Spectrometry

Background:

• Amino sugars, like d-galactosamine (G), are crucial in biological systems.
• Discriminating chiral molecules requires sophisticated analytical techniques.
• Supramolecular complexes can be designed for selective guest binding and reactivity modulation.

Purpose of the Study:

• To investigate the discrimination of d-galactosamine (G) using enantiomers of cyclochiral resorcin[4]arenes (C).
• To probe the reactivity of [C·H·G]+ proton-bound complexes with primary amines (B).
• To understand how supramolecular architecture and cyclochirality influence guest-host interactions and reactivity.

Main Methods:

• Nano-ESI-FT-ICR mass spectrometry was employed to generate and analyze proton-bound complexes.
• Complexes of d-galactosamine (G) with resorcin[4]arene enantiomers (C) were formed.
• Reactions of these complexes with various primary amines (B) were studied to observe ligand exchange and isomerization.

Main Results:

• Three types of [C·H·G]+ aggregates were identified ([C·H·G]+ESI, [C·H·G]+GAS, [C·H·G]+SOL), exhibiting distinct origins and reactivities.
• Electrospray-generated adducts ([C·H·G]+ESI) underwent ligand exchange with amines and partial isomerization.
• A cyclochirality effect on reactivity was observed, dependent on the specific aggregate type.

Conclusions:

• The study successfully demonstrated the discrimination of d-galactosamine using chiral resorcin[4]arene hosts.
• The reactivity of the supramolecular complexes is tunable by the basicity of the amine guest and influenced by the complex's formation environment.
• Cyclochirality plays a significant role in modulating the reactivity of these host-guest systems.