Design and Synthesis of α-Anomeric Diacetylene-Containing Glycosides as Photopolymerizable Molecular Gelators

Abstract

Glycolipids with diacetylene functional groups are fascinating compounds with many practical uses. Among these, diacetylene-containing gelators are especially important because they can form photopolymerizable gels, which are useful stimuli-responsive materials. Inspired by the unique properties of diacetylene-containing gelators and to understand the structural influences especially the location of the diacetylene functional groups on the self-assembling properties, a series of 15 novel N -acetyl- d -glucosamine derivatives with the diacetylene functional group introduced at the anomeric position were designed and synthesized. The diacetylene function is attached to the sugar through α-glycosylation with the distance from the anomeric oxygen being varied from one, two, and three methylene groups, and the other side contains hydroxyl, carboxyl, phenyl, and alkyl substituents. Remarkably, all compounds can form self-assembled gels in one or more selected solvents. A majority of these synthesized diacetylene glycosides are effective gelators for ethanol/water (v/v 1:1), dimethyl sulfoxide/water (v/v 1:1), and toluene, and one compound also formed a hydrogel at 1.0 wt %. Typically, these glycosides form gels that are photopolymerizable to afford red-colored gels. Scanning electronic microscopy indicated that the gelators formed helices, fibers, and planar sheet-like morphologies. The chemical structures of the derivatives affected their gelation properties and responses to UV treatment. The carboxylic acid-functionalized derivative 17 was able to immobilize basic solutions and form transparent gels. We expect that these diacetylene glycosides especially the hydroxyl and carboxylic acid derivatives will be useful as stimuli-responsive glycolipids for biomedical research.

Synthetic approaches of carbohydrate based self-assembling systems

“…The preparation of glycoamphiphiles 273 and 275 started from the glycosylation of tetra-O-acetyl-α-D-mannopyranosyl trichloroacetimidate 270 with 4,4-dihydroxylazobenzene to afford the azobenzene-containing glycoside 271, which serves as the A library of novel α-anomeric diacetylene-containing glycosides 277-279 was designed and synthesized, in which one, two, and three methylene spacers were inserted between the anomeric oxygen and diacetylene group (Scheme 41). 127 Glycosylation of N-acetyl-D-glucosamine with terminal alkynyl alcohols furnished α-alkynyl glycosides 276. Subsequent CuClcatalyzed Cadiot-Chodkiewicz coupling completed the synthesis of the glycosides 277-279.…”

“…A library of novel α-anomeric diacetylene-containing glycosides 277–279 was designed and synthesized, in which one, two, and three methylene spacers were inserted between the anomeric oxygen and diacetylene group (Scheme 41). 127 Glycosylation of N -acetyl- d -glucosamine with terminal alkynyl alcohols furnished α-alkynyl glycosides 276 . Subsequent CuCl-catalyzed Cadiot–Chodkiewicz coupling completed the synthesis of the glycosides 277–279 .…”

Recent advances in carbohydrate-based gelators

“…62, could be used as stimulus-responsive materials, which are highly advantageous in biomedical applications. 125 In another work, a highly environment-friendly and biologically safe cross-linker, oxidized sucrose (OS) was used to form carboxymethyl chitosan hydrogel (CMCG) 102 (Fig. 63) of a polysaccharide, carboxymethyl chitosan (CMC).…”

“…62, could be used as stimulus-responsive materials, which are highly advantageous in biomedical applications. 125…”

Green carbon–carbon homocoupling of terminal alkynes by a silica supported Cu(ii)-hydrazone coordination compound

“…There are several methods for the synthesis of diacetylenes 10 among which the coupling of terminal alkynes with copper catalysts is one of the most important methods for this process. 11 Various copper catalysts like copper salts in +1 and +2 oxidation states, 12 copper Schiff base coordination compounds, 13 copper nano-particles, 14 etc .…”