Smart supramolecular photoresponsive gelator with long-alkyl chain azobenzene incorporated sugar derivatives for recycling aromatic solvents and sequestration of cationic dyes.

Phase-selective gelation of low molecular-weight photoresponsive organogelator possessing long aliphatic chain azobenzene sugar derivatives and its applications in the recycling of aromatic solvents and also the removal of cationic dyes is reported. Very low critical gelation concentration (CGC) in aromatic solvents implies that it acts as a very good gelator. The photoinduced gel-to-sol transition was attained by irradiation with UV light at 350 nm. These organogels work as a selective adsorbent for efficiently removing cationic dyes from individual aqueous dye solutions and in a mixture of cationic and anionic dye solutions show more than 95% removal within 12 h. These insights indicate that these sugar derivatives could be exploited in implementing smart materials for environmental remediation.

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

Simple, effective, and eco-friendly sugar-based phase-selective gelators were synthesized at a low cost. They showed high gelling ability toward a wide range of solvents at lower concentrations (minimum gelation concentration ∼0.3%). Preliminary tests reveal that these low molecular weight organogelators can immediately and phase-selectively gel benzene, toluene, petrol, and kerosene in water at room temperature. We also identified G13 in toluene as the good gelator, and the corresponding organogel proficiently removes water-soluble dyes from their concentrated aqueous solutions. This efficient removal of toxic organic solvents and dyes from water suggests promising applications in removing organic substances from contaminated water resources. The thermoreversible gel exhibits effective rechargeability up to five cycles of burning and gelation, which imply the flame stability of the gel. Interestingly, these compounds had a high detection ability toward Cu2+ ions with a state change from gel to the solution. The physical justification for gelation mechanisms and the molecular interaction with metal ions were further confirmed by computational studies.

Sugar-benzohydrazide based phase selective gelators for marine oil spill recovery and removal of dye from polluted water.

The synthesis of 3,4,5-tri-O-benzohydrazide based N-glycosylamines were characterized using NMR (1H and 13C) and mass spectral analysis. Gelation properties of the synthesized molecules in different solvents and oils were studied and gelation was observed with minimum Critical Gelator Concentration (CGC) of 0.8% (w/v) in benzene. The free hydroxyl group of the sugar moiety, benzohydrazide and three alkyl chains present in all these compounds afford the collective driving forces for gelation. Phase-Selective Organo-Gelators (PSOGs) are molecules that can gel the oil selectively from the biphasic combination of oil and water and it is one of the good candidates for recovering oil in case of oil spill. It is observed that these gelators can be used as solid particles on a biphasic system consist of oil and water. It solidifies the oil selectively which can be taken out by means of the physical process. FT-IR and UV-Vis spectroscopy suggest that the driving forces for the gelation are hydrogen-bonding, π-π stacking and van der Waals interaction. The gels were studied using FE-SEM, DSC and rheological techniques. FE-SEM analysis shows that the formation of thin fibers and large wrinkle like aggregate structure in the gel state is due to the presence of different weak molecular interactions. The phase selection and gel-sol transition properties of these molecules confer their ability to absorb and release dyes with high efficiency.

A concise pathway to synthesize a novel class of pyrido(2,3-d)pyrimidine-C-ß-D-glycosides.

A concise pathway to synthesize a novel class of nine different pyrido(2,3-d)pyrimidine-C-ß-d-glycosides is reported. Formation of Michael adduct as an intermediate followed by heterocyclization are the key steps and the products were characterized by different spectral studies. ß-Anomeric forms of C-glycosides were assigned from 1H NMR spectroscopy.

A facile one-pot synthesis of biphenyl methyl-C-ß-D-glycosides.

Facile one-pot synthesis of biphenyl methyl-C-ß-D-glycosides was carried out using 4,6-O-protected-C-glycoside, aromatic aldehydes and malononitrile in pyrrolidine as an organocatalyst. Studies reveal that the use of pyrrolidine resulted in a better yield.

A novel class of sugar-based ether-linked-dispirooxindolo-pyrrolidines/pyrrolizidines through [3+2]-cycloaddition of azomethine ylides.

An efficient one-pot synthesis of novel sugar based dispirooxindolo-pyrrolidines/pyrrolizidines has been accomplished by a [3+2]-cycloaddition. This method utilizes an azomethine ylide derived from isatin and sarcosine/l-proline, with an ether linked α-,ß-unsaturated-ß-C-glycosidic ketones as the dipolarophile. All these sugar-based heterocyclics were characterized by NMR ((1)H and (13)C) and elemental analysis. Antimicrobial studies of sugar based dispiroheterocyclic compound 10 shows excellent activity against different microbes.

Studies on a novel class of triaryl pyridine N-glycosylamine amphiphiles as super gelators.

A novel class of six different triaryl pyridine N-glycosylamine amphiphiles was synthesised and characterized based on different spectral techniques, such as NMR and mass analysis. Gelation properties in different aromatic and aliphatic solvents were studied and gelation was observed predominantly in aliphatic solvents with CGC of 0.5% (w/v) and is attributed to the presence of long alkyl chain. All the gels thus obtained were studied using FE-SEM and powder XRD techniques which reveal fibrous entanglement of the molecules in the gel state with intermolecular spaces of 3.62 nm and 0.43 nm.

FACE-selective fluorogenic cycloaddition reaction between coumarin azides and sugar terminal alkynes: an experimental and computational study.

Copper catalyzed azide-alkyne cycloaddition reaction (CuAAC) of non-fluorescent coumarin azides and sugar terminal alkynes afforded intense fluorescent 1,2,3-triazoles in 75-85% of yield. The photophysical properties of coumarin-sugar triazoles influenced greatly, upon introducing different substituents at 6th and 7th positions. The experimental observations were further supported by TD-DFT computational studies.

Studies on the synthesis and the antimicrobial and antioxidant activities of a novel class of fluorescein-based glycosides.

Facile glycosylation of a fluorescein diol derivative with per-O-acetyl/benzoyl sugar derivatives using BF(3)·Et(2)O catalyst resulted in the formation of the expected glycosides in 54-66% yield. The biological screening of the glycosides against different microbes shows good inhibitory activity. The antioxidant activity of the fluorescein-based glycosides shows remarkable inhibition (IC(50) ∼80%).

A facile synthesis of sugar-pyrazole derivatives.

A facile synthesis of sugar-pyrazole derivatives has been accomplished by condensation of sugar-chalcone with hydrazine hydrate under neutral conditions resulting in yields of 70-85%. The products are characterized by FTIR and NMR spectroscopy and by elemental analysis. The ß-anomeric forms for these derivatives were assigned by NMR spectroscopy.