01838nas a2200265 4500008004100000022001400041245007400055210006900129260008600198300001400284490000600298520092700304653001701231653003301248653001201281653001901293653001201312100002101324700002401345700002201369700002201391700002901413700002201442856010801464 2013 eng d a1860-539700aC-C Bond formation catalyzed by natural gelatin and collagen proteins0 aCC Bond formation catalyzed by natural gelatin and collagen prot aTRAKEHNER STRASSE 7-9, FRANKFURT AM MAIN, 60487, GERMANYbBEILSTEIN-INSTITUTcJUN a1111-11180 v93 a

The activity of gelatin and collagen proteins towards C-C bond formation via Henry (nitroaldol) reaction between aldehydes and nitroalkanes is demonstrated for the first time. Among other variables, protein source, physical state and chemical modification influence product yield and kinetics, affording the nitroaldol products in both aqueous and organic media under mild conditions. Significantly, the scale-up of the process between 4-nitrobenzaldehyde and nitromethane is successfully achieved at 1 g scale and in good yield. A comparative kinetic study with other biocatalysts shows an increase of the first-order rate constant in the order chitosan < gelatin < bovine serum albumin (BSA) < collagen. The results of this study indicate that simple edible gelatin can promote C-C bond forming reactions under physiological conditions, which may have important implications from a metabolic perspective.

10abiocatalysis10acarbon-carbon bond formation10agelatin10aHenry reaction10aprotein1 aKuehbeck, Dennis1 aDhar, Basab, Bijayi1 aSchoen, Eva-Maria1 aCativiela, Carlos1 aGotor-Fernandez, Vicente1 aDiaz, David, Diaz uhttps://library.ncl.res.in/content/c-c-bond-formation-catalyzed-natural-gelatin-and-collagen-proteins-002716nas a2200217 4500008004100000022001400041245014200055210006900197260011000266300001400376490000600390520182000396100001802216700002602234700002402260700002202284700001702306700002102323700002202344856013202366 2013 eng d a2050-748800aOrganophotocatalysis in nanostructured soft gel materials as tunable reaction vessels: comparison with homogeneous and micellar solutions0 aOrganophotocatalysis in nanostructured soft gel materials as tun aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB a4577-45880 v13 a

Riboflavin tetraacetate-catalyzed aerobic photooxidation of 1-(4-methoxyphenyl)ethanol was investigated as a model reaction under blue visible light in different soft gel materials, aiming to establish their potential as reaction vessels for photochemical transformations. Three strategies involving different degrees of organization of the catalyst within the gel network were explored, and the results compared to those obtained in homogeneous and micellar solutions. In general, physical entrapment of both the catalyst and the substrate under optimized concentrations into several hydrogel matrices (including low-molecular-weight and biopolymer-based gels) allowed the photooxidation with conversions between 55 and 100% within 120 min (TOF similar to 0.045-0.08 min(-1); k(obs) similar to 0.011-0.028 min(-1)), albeit with first-order rates ca. 1-3-fold lower than in solution under comparable non-stirred conditions. Remarkably, the organogel made of a cyclohexane-based bisamide gelator in CH3CN not only prevented the photodegradation of the catalyst but also afforded full conversion in less than 60 min (TOF similar to 0.167 min(-1); k(obs) similar to 0.073 min(-1)) without the need of additional proton transfer mediators (e. g., thiourea) as it occurs in CH3CN solutions. In general, the gelators could be recycled without detriment to their gelation ability and reaction rates. Moreover, kinetics could be fine-tuned according to the characteristics of the gel media. For instance, entangled fibrillar networks with relatively high mechanical strength were usually associated with lower reaction rates, whereas wrinkled laminated morphologies seemed to favor the reaction. In addition, the kinetics results showed in most cases a good correlation with the aeration efficiency of the gel media.

1 aBachl, Jurgen1 aHohenleutner, Andreas1 aDhar, Basab, Bijayi1 aCativiela, Carlos1 aMaitra, Uday1 aKoenig, Burkhard1 aDiaz, David, Diaz uhttps://library.ncl.res.in/content/organophotocatalysis-nanostructured-soft-gel-materials-tunable-reaction-vessels-comparison-001837nas a2200157 4500008004100000022001400041245012400055210006900179260011000248300001600358490000600374520112900380100001601509700002401525856013001549 2014 eng d a2046-206900aGreen synthesis of noble metal nanoparticles using cysteine-modified silk fibroin: catalysis and antibacterial activity0 aGreen synthesis of noble metal nanoparticles using cysteinemodif aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcSEP a46285-462920 v43 a

Noble metal nanoparticles (NPs) have shown remarkable potential for numerous applications. In this work, a simple, one-pot, green method for the synthesis of gold, silver, palladium, and platinum NPs by using thiol-modified silk fibroin (SF-SH) has been described. The incorporation of thiol groups into silk fibroin (SF) yields small, mono-dispersed metal nanoparticles with good colloidal stability. UV-Vis, transmission electron microscopy (TEM), and X-ray powder diffraction (XRD) analyses show the formation of NPs, and thermo-gravimetric analysis (TGA) data reveal interaction of the NPs with thiol-modified SF. We also show that all the NP-SF conjugates catalyse the reduction of p-nitrophenol to p-aminophenol in the presence of NaBH4 at room temperature. The NP-SF conjugate materials were processed into different material formats like porous scaffolds and films without compromising their individual properties. The Au-SF-SH composite scaffold was used successfully in the heterogeneous catalysis of p-nitrophenol reduction using NaBH4 while the Ag-SF-SH conjugated film showed good antibacterial activity.

1 aDas, Soumen1 aDhar, Basab, Bijayi uhttps://library.ncl.res.in/content/green-synthesis-noble-metal-nanoparticles-using-cysteine-modified-silk-fibroin-catalysis-001998nas a2200169 4500008004100000022001400041245015000055210006900205260000900274300001600283490000600299520133400305100002001639700001501659700002401674856013001698 2020 eng d a2470-134300aPhosphorous-doped graphitic material as a solid acid catalyst for microwave-assisted synthesis of beta-ketoenamines and baeyer-villiger oxidation0 aPhosphorousdoped graphitic material as a solid acid catalyst for cJUL  a15962-159720 v53 a

Synthesis of phosphorous-doped graphitic materials (P-Gc) using phytic acid as a precursor was done in a microwave oven in a cost- and time-effective green way. The material was used as a solid acid catalyst for microwave (MW)-assisted synthesis of beta-ketoenamines and Baeyer-Villiger (By) oxidation. In the case of BV oxidation, hydrogen peroxide (H2O2) was used as a green oxidant. For beta-ketoenamines, in most cases, 100% conversion with an similar to 95% yield was achieved in ethyl acetate medium. In solvent-free conditions, the yield of beta-ketoenamines was similar to 75%. A kinetic study suggested that the resonance stabilization of the positive reaction center happens in the transition state for beta-ketoenamine synthesis. In BV oxidation, cyclic ketones were converted to their corresponding cyclic esters in good to high yields (similar to 80% yield) in a shorter reaction time (6-20 min). As per our knowledge, this is the first report of BV oxidation catalyzed by a heteroatom-doped graphitic material. For BV oxidation, the phosphoric acid functional groups present in P-Gc might increase the electrophilicity of the carbonyl group of the ketones to compensate for the weakness of H2O2 as a nucleophile and a spiro-bisperoxide intermediate has been identified in high-resolution mass spectrometry.

1 aMaity, Sayantan1 aRam, Farsa1 aDhar, Basab, Bijayi uhttps://library.ncl.res.in/content/phosphorous-doped-graphitic-material-solid-acid-catalyst-microwave-assisted-synthesis-beta