4,6-O-Phenylethylidene Acetal Protected D-Glucosamine Carbamate-Based Gelators and Their Applications for Multi-Component Gels

Abstract

The self-assembly of carbohydrate-based low molecular weight gelators has led to useful advanced soft materials. The interactions of the gelators with various cations and anions are important in creating novel molecular architectures and expanding the scope of the small molecular gelators. In this study, a series of thirteen new C-2 carbamates of the 4,6-O-phenylethylidene acetal-protected D-glucosamine derivatives has been synthesized and characterized. These compounds are rationally designed from a common sugar template. All carbamates synthesized were found to be efficient gelators and three compounds are also hydrogelators. The resulting gels were characterized using optical microscopy, atomic force microscopy, and rheology. The gelation mechanisms were further elucidated using 1H NMR spectroscopy at different temperatures. The isopropyl carbamate hydrogelator 7 formed hydrogels at 0.2 wt% and also formed gels with several tetra alkyl ammonium salts, and showed effectiveness in the creation of gel electrolytes. The formation of metallogels using earth-abundant metal ions such as copper, nickel, iron, zinc, as well as silver and lead salts was evaluated for a few gelators. Using chemiluminescence spectroscopy, the metal–organic xerogels showed enzyme-like properties and enhanced luminescence for luminol. In addition, we also studied the applications of several gels for drug immobilizations and the gels showed sustained release of naproxen from the gel matrices. This robust sugar carbamate-derived gelator system can be used as the scaffold for the design of other functional materials with various types of applications.

Synthetic approaches of carbohydrate based self-assembling systems

“…The gelator 15 (when R′ = p -methoxyl benzyl) formed spontaneous gels when adding aqueous solutions of metal ions to the gelator solution dissolved in a small amount of DMSO. Wang's group also reported several C-2 N -linked carbamates of the 4,6- O -phenylethylidene acetal protected d -glucosamine derivatives 16 , 18 which were prepared by commercially available chloroformate and the previous literature-reported amine headgroup. 19 Among the synthesized carbamates, the isopropyl derivative ( 16 , R = iPr) is a hydrogelator and can form hydrogel at 0.2 wt%.…”

“…Wang group also reported several C-2 N-linked carbamates of the 4,6-O-phenylethylidene acetal protected D-glucosamine derivatives 16, which was prepared by commercially available chloroformate and previous literature reported amine headgroup. 18 Among the synthesized carbamates, the isopropyl derivative (16, R = iPr) is a hydrogelator and can form hydrogel at 0.2 wt%. This hydrogelator gels with tetra alkyl ammonium salts to create effective gel electrolytes.…”

Recent advances in carbohydrate-based gelators

“…Further, synthesis of C-2 carbamates of para -phenylethylidene acetal-protected d -glucosamine derivatives 124 was also reported along with their gelation properties. The study also reported isopropyl carbamate as a highly efficient hydrogelator, which also exhibited the ability to form gel electrolytes.…”

Sugar-Based Phase-Selective Supramolecular Self-Assembly System for Dye Removal and Selective Detection of Cu2+ Ions

“…Since carbohydrates are biocompatible, biodegradable, rich in stereochemistry, nontoxic, eco-friendly, inexpensive, and moreover derived from abundant renewable resources, they have proven to be an ideal choice for the development of organogels compared with other gel types . Carbohydrate-derived organogelators display applications in various fields, such as oil-spill recovery, semiconducting fabrics, CO 2 absorption, generation of nanocomposite materials, soft-optical devices, separating biomolecules, lectin binding, controlled drug encapsulation, release and delivery, self-healing, metal ion detection, and many others. − …”