Synthesis and Characterization of Monosaccharide-Derived Carbamates as Low-Molecular-Weight Gelators

Abstract

Sugar-based low-molecular-weight gelators are an interesting new class of compounds that are important in supramolecular chemistry and for the preparation of advanced materials. Previously, we synthesized a series of ester and carbamate derivatives of 4,6-O-benzylidene methyl-alpha-D-glucopyranoside and found that monosubstituted alkynyl esters with five to seven carbons and monosubstituted carbamates with saturated five- and seven-carbon chains are good gelators. To understand the structural requirement for the gelation of the carbamate derivatives (O-linked carbamates), a diverse series of analogs, including alkynyl, aryl, and alkyl halide derivatives, were prepared and analyzed. We found that for gelation the O-linked carbamate derivatives have different structural preferences than the ester derivatives. To exhibit gellation, the ester analogs favor alkyl-containing terminal acetylene groups and the carbamoyl derivatives prefer saturated hydrocarbons. Both the esters and the carbamates showed good gelation properties when they were functionalized with aryl side chains. We also synthesized and screened a new series of carbamates (N-linked carbamates) in which the nitrogen atom of the carbamate group is directly attached to the sugar ring. The N-linked carbamates are good gelators for aqueous DMSO and ethanol solutions, and two of the compounds are also able to form gels in pure water. Optical microscopy and scanning electron microscopy were used to characterize several representative gels. In general, long, narrow, uniform fibrous networks were observed for effective gelators. The structure-gelation correlation obtained here can be used in the design of new sugar-based low-molecular-weight gelators.

Versatile Supramolecular Gelators That Can Harden Water, Organic Solvents and Ionic Liquids

“…Several groups also investigated the gelation of water/organic solvent mixture using supramolecular gelators. 3,6,7 Peptide amphiphiles (PAs) are one of the most studied supramolecular gelators for hydrogenation. Stupp et al reported a wide variety of PA-based supramolecular gelators with various functional properties and proposed their biological applications.…”

Charge-transfer interaction mediated organogels from 18β-glycyrrhetinic acid appended pyrene

“…In order to control the molecular arrangement in 1D structures, low molecular weight gelators (LMWGs) have generated considerable interest during the past decade [5–6]. The driving forces for the formation of such self-assembled fibrillar networks include hydrogen-bonding interaction, van der Waals force, π–π stacking, and donor–acceptor interaction [7–10]. Since LMWGs are often thermally reversible and the gelation can be triggered by pH or the addition of small molecules (cations, anions), they can potentially be used in biomedicine [11–13], sensing [14–15], optoelectronics [16–17], and other applications [18–19].…”

Supramolecular Hydrogels Made of Basic Biological Building Blocks

“…For example, the N-linked carbamates ( 83 , 84) , in which the nitrogen atom of the carbamate group is directly attached to the sugar ring, self-assemble to form gels in pure water with long, narrow, uniform fibrous networks at the mgc about 0.5 wt%. [139] The replacement of N-linked to the O-linked carbamates or change in the position of the side chains on the sugar ring still affords excellent hydrogelators (e.g., 85 , 86 , 87 , and 88 ), [140] which form self-assembled network structures. Although the gelation properties depend on the acyl chain length and the structures of the head groups, these results indicate that the aromatic-aromatic interactions among the gelators and intermolecular hydrophobic interactions contribute to the hydrogelation.…”