01985nas a2200253 4500008004100000022001400041245011600055210006900171260007300240300001200313490000800325520103000333653002401363653002401387653002701411653001101438653002801449100001901477700003501496700003001531700001901561700002601580856012501606 2011 eng d a0926-860X00aSelective hydrogenation of chloronitrobenzenes with an MCM-41 supported platinum allyl complex derived catalyst0 aSelective hydrogenation of chloronitrobenzenes with an MCM41 sup aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAY a117-1250 v3993 a

A platinuin precatalyst (1) has been prepared by reacting [(eta(3)-C3H5)(4)Pt4Cl4] with surface functionalized MCM-41 with pendant -(CH2)(3)NH(CH2)(2)NH2 groups. For the hydrogenation of o-, m- and p-chloronitrobenzenes to the corresponding chloroanilines, 1 is found to be a highly active catalyst with good selectivities for them-and p-isomers. Its performance is superior to that of its palladium analogue and far superior to that of commercial (5%) Pt/C or (5%) Pt/Al2O3. Comparison of solid state and solution NMR data and other evidences indicate that on treatment with the functionalized MCM-41 support; [(eta(3)-C3H5)(4)Pt4Cl4] loses the ally! ligand. XPS data show that in the fresh catalyst Pt is present in the 2+ oxidation state. Based on these and analytical data, co-ordination by surface diamine and hydroxo groups to Pt2+ in 1 is suggested. In the used catalyst both Pt2+ and Pt are present but the amount of metallic platinum is similar to 16% of the total. (C) 2011 Elsevier B.V. All rights reserved.

10aChloronitrobenzenes10aDehydrohalogenation10aheterogeneous catalyst10aMCM-4110aSelective hydrogenation1 aIndra, Arindam1 aRajamohanan, Pattuparambil, R.1 aGopinath, Chinnakonda, S.1 aBhaduri, Sumit1 aLahiri, Goutam, Kumar uhttps://library.ncl.res.in/content/selective-hydrogenation-chloronitrobenzenes-mcm-41-supported-platinum-allyl-complex-001950nas a2200265 4500008004100000022001400041245012600055210006900181260007700250300001600327490000700343520093400350653002701284653001601311653003601327653001301363653002501376100002201401700002401423700002601447700002201473700003501495700002401530856013001554 2011 eng d a0947-653900aSynthesis and structural characterization of homochiral homo-oligomers of parent CIS- and trans-furanoid-beta-amino acids0 aSynthesis and structural characterization of homochiral homoolig aPO BOX 10 11 61, D-69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcNOV a12946-129540 v173 a

The synthesis of homochiral homo-oligomers of cis- and trans-3-aminotetrahydrofuran-2-carboxylic acids (parent cis- and trans-furanoid-beta-amino acids, referred to as ``cis-/trans-FAA'') has been carried out to understand their secondary structures and their dependence on the ring heteroatom. The oligomers of two diastereomers have been shown to have a distinct left-handed helicity. The cis-FAA homo-oligomers show a 14-helix structure, in contrast to the homo-oligomers of cis-ACPC, which adopt a sheet like structure. The trans-FAA homo-oligomers were found to adopt a 12-helix structure, the same trend found in trans-ACPC homo-oligomers. With the help of ab initio calculations, the structural features of cis-ACPC and cis-FAA hexamers were compared. We believe that the more compact packing of the cis-FAA hexapeptide should be due to a more favorable interaction between the ring and the backbone amide hydrogen.

10aab initio calculations10aAmino acids10aDensity functional calculations10aPeptides10asecondary structures1 aPandey, Sunil, K.1 aJogdand, Ganesh, F.1 aOliveira, Joao, C. A.1 aMata, Ricardo, A.1 aRajamohanan, Pattuparambil, R.1 aRamana, Chepuri, V. uhttps://library.ncl.res.in/content/synthesis-and-structural-characterization-homochiral-homo-oligomers-parent-cis-and-trans-001333nas a2200205 4500008004100000022001400041245012700055210006900182260011000251300001400361490000700375520044900382100002500831700003300856700002400889700002400913700003500937700002800972856012701000 2013 eng d a1477-052000aSwitching the H-bonding network of a foldamer by modulating the backbone chirality and constitutional ratio of amino acids0 aSwitching the Hbonding network of a foldamer by modulating the b aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcNOV a7072-70750 v113 a

This communication describes the folding propensity of a hetero-foldamer motif featuring proline (Pro) and anthranilic acid (Ant) residues in a 1:2:1 (alpha: beta: alpha) constitutional ratio. Structural investigations unequivocally suggest that the hydrogen-bonding network of this foldamer motif can be switched between 9-membered and 6-membered by modulating the backbone chirality and constitutional ratio of the amino acid residues.

1 aRamesh, Veera, V. E.1 aVijayadas, Kuruppanthara, N.1 aDhokale, Snehal, A.1 aGonnade, Rajesh, G.1 aRajamohanan, Pattuparambil, R.1 aSanjayan, Gangadhar, J. uhttps://library.ncl.res.in/content/switching-h-bonding-network-foldamer-modulating-backbone-chirality-and-constitutional-001793nas a2200241 4500008004100000022001400041245013800055210006900193260007100262300001600333490000800349520084600357100002101203700002001224700002301244700002201267700002401289700002401313700002601337700003501363700002801398856012501426 2013 eng d a0002-786300aSynthetic zipper peptide motif orchestrated via co-operative interplay of hydrogen bonding, aromatic stacking, and backbone chirality0 aSynthetic zipper peptide motif orchestrated via cooperative inte a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAUG a11477-114800 v1353 a

Here, we report on a new class of synthetic zipper peptide which assumes its three-dimensional zipper-like structure via a co-operative interplay of hydrogen bonding, aromatic stacking, and backbone chirality. Structural studies carried out in both solid- and solution-state confirmed the zipper-like structural architecture assumed by the synthetic peptide which makes use of unusually remote inter-residual hydrogen-bonding and aromatic stacking interactions to attain its shape. The effect of chirality modulation and the extent of noncovalent forces in the structure stabilization have also been comprehensively explored via single-crystal X-ray diffraction and solution-state NMR studies. The results highlight the utility of noncovalent forces in engineering complex synthetic molecules with intriguing structural architectures.

1 aNair, Roshna, V.1 aKheria, Sanjeev1 aRayavarapu, Suresh1 aKotmale, Amol, S.1 aJagadeesh, Bharatam1 aGonnade, Rajesh, G.1 aPuranik, Vedavati, G.1 aRajamohanan, Pattuparambil, R.1 aSanjayan, Gangadhar, J. uhttps://library.ncl.res.in/content/synthetic-zipper-peptide-motif-orchestrated-co-operative-interplay-hydrogen-bonding-002266nas a2200229 4500008004100000022001400041245015400055210006900209260009900278300001200377490000800389520136000397653002101757653001401778653001801792653000801810653001001818100002501828700003501853700002301888856012501911 2014 eng d a0144-861700aSupramolecular transitions in native cellulose-I during progressive oxidation reaction leading to quasi-spherical nanoparticles of 6-carboxycellulose0 aSupramolecular transitions in native celluloseI during progressi aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcNOV a615-6230 v1133 a

Cellulose-I swells considerably in phosphoric acid, and converts to amorphous cellulose via a cellulose-II transition state. Controlled oxidation of cellulose-I to 6-carboxycellulose (6CC) using HNO3-H3PO4-NaNO2 oxidation system led to the selective production of 6CC's of varying carboxyl contents (1.7-22%) as well as various shapes and sizes (macro-sized fibrils of several micron length and/or spherical nanoparticles of 25-35 nm), depending on the reaction conditions. 6CC's having less than 14% carboxyl content were largely in cellulose-II form (WAXRD values in-between cellulose I and cellulose II), whereas at 14-22% the 6CC's were largely amorphous; only trace crystallinity was observed at 19% and 22% carboxyl 6CC. Spherical nanoparticles retained a high degree of crystallinity having cellulose-I structure, whereas the macro-sized fibrils were largely converted to cellulose-II structure. Analysis by WAXRD as well as by CP-MAS C-13 NMR studies gave similar conclusions. Reduced molecular weight with progressive oxidation, including presence of oligomers, was also evident from an increase in the reducing-end carbon peak at similar to 92 ppm. For high oxidation levels (>14%) the NMR 92-96 ppm peaks disappeared on extracting with dilute alkali, due to soluble oligomers being removed. (C) 2014 Elsevier Ltd. All rights reserved.

10aCarboxycellulose10acellulose10aNanoparticles10aNMR10aWAXRD1 aSharma, Priyanka, R.1 aRajamohanan, Pattuparambil, R.1 aVarma, Anjanikumar uhttps://library.ncl.res.in/content/supramolecular-transitions-native-cellulose-i-during-progressive-oxidation-reaction-001955nas a2200217 4500008004100000022001400041245007700055210006900132260000800201300001400209490000700223520124600230100001701476700001701493700002101510700002601531700003501557700002101592700001701613856010701630 2016 eng d a1525-779700aSilk fibroin-sophorolipid gelation: deciphering the underlying mechanism0 aSilk fibroinsophorolipid gelation deciphering the underlying mec cOCT a3318-33270 v173 a

Silk fibroin (SF) protein, produced by silkworm Bombyx mori, is a promising biomaterial, while sophorolipid (SL) is an amphiphilic functional biosurfactant synthesized by nonpathogenic yeast Candida bombicola. SL is a mixture of two forms, acidic (ASL) and lactonic (LSL), which when added to SF results in accelerated gelation of silk fibroin. LSL is known to have multiple biological functionalities and hence hydrogels of these green molecules have promising applications in the biomedical sector. In this work, SANS, NMR, and rheology are employed to examine the assembling properties of individual and mixed SLs and their interactions with SF to understand the mechanism that leads to rapid gelation. SANS and NMR studies show that ASL assembles to form charged micelles, while LSL forms micellar assemblies and aggregates of a mass fractal nature. ASL and LSL together form larger mixed micelles, all of which interact differently with SF. It is shown that preferential binding of LSL to SF causes rapid unfolding of the SF chain leading to the formation of intermolecular beta sheets, which trigger fast gelation. Based on the observations, a mechanism for gelation of SF in the presence of different sophorolipids is proposed.

1 aDubey, Parul1 aKumar, Sugam1 aAswal, Vinod, K.1 aRavindranathan, Sapna1 aRajamohanan, Pattuparambil, R.1 aPrabhune, Asmita1 aNisal, Anuya uhttps://library.ncl.res.in/content/silk-fibroin-sophorolipid-gelation-deciphering-underlying-mechanism02509nas a2200241 4500008004100000245014200041210006900183260000800252300001400260490000700274520163100281100001701912700002401929700002401953700001601977700001701993700001902010700003502029700002202064700003002086700002402116856012702140 2017 eng d00aSecondary interactions arrest the hemiaminal intermediate to invert the modus operandi of schiff base reaction: a route to benzoxazinones0 aSecondary interactions arrest the hemiaminal intermediate to inv cAPR a4342-43510 v823 aDiscovered by Hugo Schiff, condensation between amine and aldehyde represents one of the most ubiquitous reactions in chemistry. This classical reaction is widely used to manufacture pharmaceuticals and fine chemicals. However, the rapid and reversible formation of Schiff base prohibits formation of alternative products, of which benzoxazinones are an important class. Therefore, manipulating the reactivity of two partners to invert the course of this reaction is an elusive target. Presented here is a synthetic strategy that regulates the sequence of Schiff base reaction via weak secondary interactions. Guided by the computational models, reaction between 2,3,4,5,6-pentafluoro-benzaldehyde with 2-amino-6methylbenzoic acid revealed quantitative (99%) formation of 5-methyl-2-(perfluoropheny01,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (15). Electron donating and electron withdrawing ortho-substituents on 2-aminobenzoic acid resulted in the production of benzoxazinones 936. The mode of action was tracked using low temperature NMR, IN vis spectroscopy, and isotopic (O-18) labeling experiments. These spectroscopic mechanistic investigations revealed that the hemiaminal intermediate is arrested by the hydrogen-bonding motif to yield benzoxazinone. Thus, the mechanistic investigations and DFT calculations categorically rule out the possibility of in situ imine formation followed by ring-closing, but support instead hydrogen-bond assisted ring-closing to prodrugs. This unprecedented reaction represents an interesting and competitive alternative to metal catalyzed and classical methods of preparing benzoxazinone.1 aPatel, Ketan1 aDeshmukh, Satej, S.1 aBodkhe, Dnyaneshwar1 aMane, Manoj1 aVanka, Kumar1 aShinde, Dinesh1 aRajamohanan, Pattuparambil, R.1 aNandi, Shyamapada1 aVaidhyanathan, Ramanathan1 aChikkali, Samir, H. uhttps://library.ncl.res.in/content/secondary-interactions-arrest-hemiaminal-intermediate-invert-modus-operandi-schiff-base01441nas a2200229 4500008004100000245012100041210006900162260000800231300001400239490000700253520061900260100002300879700001700902700001800919700002200937700001800959700003500977700002401012700002101036700002301057856013101080 2017 eng d00aSelf-assembly of fluorinated sugar amino acid derived alpha,gamma-cyclic peptides into transmembrane anion transport0 aSelfassembly of fluorinated sugar amino acid derived alphagammac cNOV a5948-59510 v193 aSyntheses of fluorinated sugar amino acid derived alpha,gamma-cyclic tetra- and hexapeptides are reported. The IR, NMR, ESI-MS, CD, and molecular modeling studies of cyclic tetra- and hexapeptides showed C-2 and C-3 symmetric flat oval- and triangular-ring shaped, beta-strand conformations, respectively, which appear to self assemble into nanotubes. The alpha,gamma-cyclic hexapeptide (EC50 = 2.14 mu M) is found to be a more efficient ion transporter than alpha,gamma-cyclic tetrapeptide (EC50 = 14.75 mu M). The anion selectivity and recognition of alpha,gamma-cyclic hexapeptide with NO3- ion is investigated.1 aBurade, Sachin, S.1 aSaha, Tanmoy1 aBhuma, Naresh1 aKumbhar, Navanath1 aKotmale, Amol1 aRajamohanan, Pattuparambil, R.1 aGonnade, Rajesh, G.1 aTalukdar, Pinaki1 aDhavale, Dilip, D. uhttps://library.ncl.res.in/content/self-assembly-fluorinated-sugar-amino-acid-derived-alphagamma-cyclic-peptides-transmembrane02139nas a2200265 4500008004100000022001400041245015200055210006900207260000800276300001200284490000600296520121100302653002601513653002801539653001601567653001301583653002001596653001401616653001801630100001701648700003501665700002601700700001701726856013001743 2020 eng d a2637-610500aSelf-assembly of bispentadecylphenol substituted perylenediimide with PS-b-P4VP for structure-property insight into the core of core-shell micelles0 aSelfassembly of bispentadecylphenol substituted perylenediimide  cFEB a805-8160 v23 a

We report the use of a ditopic molecular probe bispentadecylphenol substituted perylenediimide (PBI-PDP) to examine the molecular level self-assembly of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) in tetrahydrofuran (THF). A series of complexes were prepared between PS-b-P4VP copolymers with varying lengths of the 4-vinylpyridine chain and PBI-PDP. Light scattering and NMR spectroscopic studies reveal that the self-assembled structures of the solid complexes are not fully disrupted when the complexes are dissolved in THF. NMR experimental parameters measured for the small probe molecule provide detailed insights into the structure of the assemblies in solution as well as the interaction between the small molecule and the block copolymer. Such insights can have important implications in manipulating the nanostructure of block copolymer micelles to suit various application requirements. The dynamics and distribution of the PBI-PDP molecules within the assemblies in solution show a dependence on the length of the P4VP block. Transmission electron microscopy was employed to study the evolution of morphologies in films prepared from the self-assembled structures in THF solutions.

10acore corona interface10aditopic molecular probe10aenvironment10amicelles10aperylenediimide10aPS-b-P4VP10aSelf-assembly1 aRoy, Moumita1 aRajamohanan, Pattuparambil, R.1 aRavindranathan, Sapna1 aAsha, S., K. uhttps://library.ncl.res.in/content/self-assembly-bispentadecylphenol-substituted-perylenediimide-ps-b-p4vp-structure-property