@article { ISI:000311966300017, title = {1-Benzoyl-3-[(2-benzylsulfanyl)phenyl]thiourea}, journal = {Acta Crystallographica Section C-Crystal Structure Communications}, volume = {68}, number = {12}, year = {2012}, month = {DEC}, pages = {O485-U254}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

In the title compound, C21H18N2OS2, a strong intramolecular N-H center dot center dot center dot O hydrogen bond [N center dot center dot center dot O = 2.642 (3) angstrom] between the amide N atom and the benzoyl O atom forms an almost planar six-membered ring in the central part of the molecule. In the crystal, molecules are packed through weak N-H center dot center dot center dot S interactions. Intra- and intermolecular hydrogen bonds and van der Waals interactions are the stabilizing forces for the crystal structure.

}, issn = {0108-2701}, doi = {10.1107/S0108270112045167}, author = {Bhattacharjee, Tirtha and Gogoi, Prasanta and Puranik, Vedavati G. and Gawade, Rupesh L. and Barman, Pranjit} } @article { ISI:000304387800025, title = {Efficient total synthesis of calothrixin B}, journal = {Tetrahedron Letters}, volume = {53}, number = {23}, year = {2012}, month = {JUN}, pages = {2894-2896}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

An efficient synthesis of calothrixin B (2) is demonstrated starting from 9H-carbazol-4-ol, having two one-pot reaction sequences as key steps. As a novel observation, DMF-methanol was shown to be a hydride donor for reduction of aldehyde to alcohol. Unexpectedly, nucleophilic substitution of benzyloxy by methoxy group was observed. (C) 2012 Elsevier Ltd. All rights reserved.

}, keywords = {Calothrixin B, CAN, DMF-methanol, Hydride donor}, issn = {0040-4039}, doi = {10.1016/j.tetlet.2012.03.131}, author = {Bhosale, Shrikar M. and Gawade, Rupesh L. and Puranik, Vedavati G. and Kusurkar, Radhika S.} } @article { ISI:000303429600017, title = {Formal synthesis of (-)-stemoamide using a useful epimerization at C-8}, journal = {Tetrahedron Letters}, volume = {53}, number = {21}, year = {2012}, month = {MAY}, pages = {2647-2650}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

The formal synthesis of (-)-stemoamide was achieved starting from L-pyroglutamic acid. The key steps used are the allylation using BF3 center dot OEt2, ring closing metathesis, allylic oxidation and a novel epimerization at C8. (C) 2012 Elsevier Ltd. All rights reserved.

}, keywords = {Allylation, Allylic oxidation, Pyroglutamic acid, Ring closing metathesis, Stemoamide}, issn = {0040-4039}, doi = {10.1016/j.tetlet.2012.03.054}, author = {Chavan, Subhash P. and Harale, Kishor R. and Puranik, Vedavati G. and Gawade, Rupesh L.} } @article { ISI:000307300900016, title = {Helical folding in heterogeneous foldamers without inter-residual backbone hydrogen-bonding}, journal = {Chemical Communications}, volume = {48}, number = {71}, year = {2012}, month = {JUL}, pages = {8922-8924}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

This communication describes a set of hybrid foldamers that do not feature inter-residual, but intra-residual backbone hydrogen-bonding, yet adopt a preferentially folded conformation displaying right-handed helical architecture. Conformational ordering is apparently due to the combined conformational restrictions imposed by the conformationally restricted individual amino acid residues with which the oligomers are made of.

}, issn = {1359-7345}, doi = {10.1039/c2cc33235c}, author = {Priya, Gowri and Kotmale, Amol S. and Gawade, Rupesh L. and Mishra, Deepti and Pal, Sourav and Puranik, Vedavati G. and Rajamohanan, Pattuparambil R. and Sanjayan, Gangadhar J.} } @article { ISI:000308628900033, title = {New synthetic route for 1,2-diketo compounds using unexpected C-C bond cleavage by PCC}, journal = {Tetrahedron Letters}, volume = {53}, number = {39}, year = {2012}, month = {SEP}, pages = {5327-5330}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

An efficient method has been established for the preparation of 1,2-diketones by unexpected C-C bond cleavage in 4-keto-2-hydroxy esters using pyridiniumchlorochromate (PCC). (c) 2012 Elsevier Ltd. All rights reserved.

}, keywords = {1, 2-Diketones, C-C bond cleavage, PCC}, issn = {0040-4039}, doi = {10.1016/j.tetlet.2012.07.095}, author = {Bhosale, Shrikar M. and Momin, Aadil A. and Gawade, Rupesh L. and Puranik, Vedavati G. and Kusurkar, Radhika S.} } @article { ISI:000311783800011, title = {Phyllocladane diterpenes from anisomeles heyneana}, journal = {Journal of Asian Natural Products Research}, volume = {14}, number = {12}, year = {2012}, month = {NOV}, pages = {1162-1168}, publisher = {TAYLOR \& FRANCIS LTD}, type = {Article}, address = {4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND}, abstract = {

New phyllocladane diterpene, phyllocladan-16 alpha,17-dihydroxy-19-oic acid (1), together with known phyllocladane diterpene, phyllocladan-16 alpha,19-diol (2), cembrane diterpene ovatodiolide (3), sitosteryl-3-O-beta-D-glucoside (4), and verbascoside (5), were isolated from aerial parts of Anisomeles heyneana. The structure of compound 1 was elucidated by 1D and 2D NMR analyses which included HSQC, HMBC, and nuclear overhauser effect spectroscopy (NOESY) experiments as well as X-ray crystallography. This is the first report of phyllocladane diterpenes from genus Anisomeles. Compounds 1, 3, 4, and 5 were evaluated for inhibition of Mycobacterium tuberculosis and 3 was found to exhibit anti-mycobacterial activity with IC90 6.53 mu g/ml. Compounds 1, 3, and 5, at 100 mu g/ml, were also evaluated for inhibition of Thp-1 cell lines, and compounds 1 and 3 showed 59.02\% and 96.4\% inhibitions, respectively.

}, keywords = {Anisomeles heyneana, Lamiaceae, Mycobacterium tuberculosis, phyllocladane diterpenes}, issn = {1028-6020}, doi = {10.1080/10286020.2012.738672}, author = {Kulkarni, Roshan R. and Shurpali, Ketaki and Gawade, Rupesh L. and Sarkar, Dhiman and Puranik, Vedavati G. and Joshi, Swati P.} } @article { ISI:000300466900006, title = {Understanding the growth of micro and nano-crystalline AlN by thermal plasma process}, journal = {Journal of Crystal Growth}, volume = {339}, number = {1}, year = {2012}, month = {JAN}, pages = {36-45}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

We report the studies related to the growth of crystalline AlN in a DC thermal plasma reactor, operated by a transferred arc plasma torch. The reactor is capable of producing the nanoparticles of Al and AlN depending on the composition of the reacting gas. Al and AlN micro crystals are formed at the anode placed on the graphite and nano crystalline Al and AlN gets deposited on the inner surface of the plasma reactor. X-ray diffraction, Raman spectroscopy analysis, single crystal X-ray diffraction and TGA-DTA techniques are used to infer the purity of post process crystals as a hexagonal AlN. The average particle size using SEM was found to be around 30 mu m. The morphology of nanoparticles of Al and AlN, nucleated by gas phase condensation in a homogeneous medium were studied by transmission electron microscopy analysis. The particle ranged in size between 15 and 80 nm in diameter. The possible growth mechanism of crystalline AlN at the anode has been explained on the basis of non-equilibrium processes in the core of the plasma and steep temperature gradient near its periphery. The gas phase species of AlN and various constituent were computed using Murphy code based on minimization of free energy. The process provides 50\% yield of microcrystalline AlN and remaining of Al at anode and that of nanocrystalline h-AlN and c-Al collected from the walls of the chamber is about 33\% and 67\%, respectively. (C) 2011 Elsevier B.V. All rights reserved.

}, keywords = {Crystal morphology, Growth from high temperature solutions, Nitride, Semiconducting aluminum compound}, issn = {0022-0248}, doi = {10.1016/j.jcrysgro.2011.11.011}, author = {Kanhe, Nilesh S. and Nawale, Ashok B. and Gawade, Rupesh L. and Puranik, Vedavati G. and Bhoraskar, S. V. and Das, Asoka K. and Mathe, Vikas L.} } @article { ISI:000308414500020, title = {Unusual conformational similarity of two peptide folds featuring sulfonamide and carboxamide on the backbone}, journal = {Chemical Communications}, volume = {48}, number = {78}, year = {2012}, month = {AUG}, pages = {9747-9749}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Two folded peptides featuring carboxamide and sulfonamide at the core of the peptide fold have been shown to possess almost similar conformational features, despite the well-known fact that carboxamides and sulfonamides have strikingly different hydrogen-bonding and geometrical preferences.

}, issn = {1359-7345}, doi = {10.1039/c2cc34533a}, author = {Vijayadas, Kuruppanthara N. and Davis, Hilda C. and Kotmale, Amol S. and Gawade, Rupesh L. and Puranik, Vedavati G. and Rajamohanan, Pattuparambil R. and Sanjayan, Gangadhar J.} } @article { ISI:000320036300013, title = {Ant-pro reverse-turn motif. structural features and conformational characteristics}, journal = {European Journal of Organic Chemistry}, number = {17, SI}, year = {2013}, month = {JUN}, pages = {3529-3542}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

This article details the characteristic conformational features of the Ant-Pro reverse turn ? a folded pseudo -turn motif that displays a closed nine-membered-ring hydrogen-bonded network involving just two amino acid residues, namely anthranilic acid (Ant; a constrained -amino acid), and proline (Pro; a constrained -amino acid). The results from the extensive investigation of ten crystal structures and their NMR conformations in the solution state provide a clear idea about the conformational characteristics of the Ant-Pro reverse turn. The Ant and Pro residues, which form the turn segment, maintain a perfect antiperiplanar orientation throughout, leaving little possibility for the formation of the otherwise possible six-membered hydrogen-bonding that requires a coplanar disposition of the two amino acid residues, as clearly evident from investigation of several crystal structures. The closed hydrogen-bonded network observed in the Ant-Pro reverse turn motif, formed in the forward direction of the sequence (12 amino acid interactions) involving only two amino acid residues, is in stark contrast to the native -turns that involve four residues to form hydrogen-bonded network featuring backward 14 amino acid interactions. The readily available two-residue Ant-Pro motif raises the possibility of a practical utility, particularly in the application of rigidifying flexible peptide backbones by inserting the robust Ant-Pro reverse turn motifs into their backbone.

}, keywords = {Peptides, Peptidomimetics, Protein folding, Protein structures}, issn = {1434-193X}, doi = {10.1002/ejoc.201201739}, author = {Thorat, Vijaykumar H. and Ingole, Tukaram S. and Vijayadas, Kuruppanthara N. and Nair, Roshna V. and Kale, Sangram S. and Ramesh, Veera V. E. and Davis, Hilda C. and Prabhakaran, Panchami and Gonnade, Rajesh G. and Gawade, Rupesh L. and Puranik, Vedavati G. and Rajamohanan, Pattuparambil R. and Sanjayan, Gangadhar J.} } @article { ISI:000317327900022, title = {Carboxamide versus sulfonamide in peptide backbone folding: a case study with a hetero foldamer}, journal = {Organic Letters}, volume = {15}, number = {7}, year = {2013}, month = {APR}, pages = {1504-1507}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Strikingly dissimilar hydrogen-bonding patterns have been observed for two sets of closely similar hetero foldamers containing carboxamide and sulfonamides at regular intervals. Although both foldamers maintain conformational ordering, the hydrogen-bonding pattern and backbone helical handedness differ diametrically.

}, issn = {1523-7060}, doi = {10.1021/ol4002762}, author = {Ramesh, Veera V. E. and Kale, Sangram S. and Kotmale, Amol S. and Gawade, Rupesh L. and Puranik, Vedavati G. and Rajamohanan, P. R. and Sanjayan, Gangadhar J.} } @article { ISI:000328182900006, title = {Ester vs. amide on folding: a case study with a 2-residue synthetic peptide}, journal = {Organic \& Biomolecular Chemistry}, volume = {11}, number = {48}, year = {2013}, month = {DEC}, pages = {8348-8356}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Although known for their inferiority as hydrogen-bonding acceptors when compared to amides, esters are often found at the C-terminus of peptides and synthetic oligomers (foldamers), presumably due to the synthetic readiness with which they are obtained using protected peptide coupling, deploying amino acid esters at the C-terminus. When the H-bonding interactions deviate from regularity at the termini, peptide chains tend to {\textquoteleft}{\textquoteleft}fray apart{\textquoteright}{\textquoteright}. However, the individual contributions of C-terminal esters in causing peptide chain end-fraying goes often unnoticed, particularly due to diverse competing effects emanating from large peptide chains. Herein, we describe a striking case of a comparison of the individual contributions of C-terminal ester vs. amide carbonyl as a H-bonding acceptor in the folding of a peptide. A simple two-residue peptide fold has been used as a testing case to demonstrate that amide carbonyl is far superior to ester carbonyl in promoting peptide folding, alienating end-fraying. This finding would have a bearing on the fundamental understanding of the individual contributions of stabilizing/destabilizing non-covalent interactions in peptide folding.

}, issn = {1477-0520}, doi = {10.1039/c3ob41967c}, author = {Vijayadas, Kuruppanthara N. and Nair, Roshna V. and Gawade, Rupesh L. and Kotmale, Amol S. and Prabhakaran, Panchami and Gonnade, Rajesh G. and Puranik, Vedavati G. and Rajamohanan, Pattuparambil R. and Sanjayan, Gangadhar J.} } @article { ISI:000315168800015, title = {Orthanilic acid-promoted reverse turn formation in peptides}, journal = {Chemical Communications}, volume = {49}, number = {22}, year = {2013}, month = {JAN}, pages = {2222-2224}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Orthanilic acid (2-aminobenzenesulfonic acid, (S)Ant), an aromatic beta-amino acid, has been shown to be highly useful in inducing a folded conformation in peptides. When incorporated into peptide sequences (Xaa-(S)Ant-Yaa), this rigid aromatic beta-amino acid strongly imparts a reverse-turn conformation to the peptide backbone, featuring robust 11-membered-ring hydrogen-bonding.

}, issn = {1359-7345}, doi = {10.1039/c3cc40522b}, author = {Kale, Sangram S. and Priya, Gowri and Kotmale, Amol S. and Gawade, Rupesh L. and Puranik, Vedavati G. and Rajamohanan, P. R. and Sanjayan, Gangadhar J.} } @article { ISI:000325738700001, title = {Sugar furanoid trans-vicinal diacid as a gamma-turn inducer: synthesis and conformational study}, journal = {Organic \& Biomolecular Chemistry}, volume = {11}, number = {40}, year = {2013}, month = {OCT}, pages = {6874-6878}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A simple method for the synthesis of a sugar furanoid trans vicinal diacid and its incorporation into the N-terminal tetrapeptide sequence (H-Phe-Trp-Lys-Thr-OH) to get glycopeptide 8 has been described. 2D NMR and MD simulation studies of 8 clearly show that the sugar diacid adopts a gamma-turn conformation towards the N-terminus.

}, issn = {1477-0520}, doi = {10.1039/c3ob41462k}, author = {Vangala, Madhuri and Dhokale, Snehal A. and Gawade, Rupesh L. and Pattuparambil, Rajamohanan R. and Puranik, Vedavati G. and Dhavale, Dilip D.} } @article {46399, title = {Additive induced capture of elusive polymorphs of conformationally flexible Sulfonamides/Sulfoesters}, journal = {Acta Crystallographica A-Foundation and Advances}, volume = {70}, year = {2014}, month = {MAY}, pages = {C776}, type = {Meeting Abstract}, keywords = {additive induced polymorphism, intermolecular interactions, phase transition}, issn = {2053-2733}, author = {Shaikh, Samir Rashid and Gawade, Rupesh L. and Chakravarty, Debamitra K. and Puranik, Vedavati G. and Gonnade, Rajesh} } @article { ISI:000331895900018, title = {Conformational modulation of peptide secondary structures using beta-aminobenzenesulfonic acid}, journal = {Chemical Communications}, volume = {50}, number = {22}, year = {2014}, month = {JAN}, pages = {2886-2888}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

This communication describes the influence of beta-aminobenzenesulfonic acid ((S)Ant) on the conformational preferences of hetero foldamers. The designed (Aib-(S)Ant-Aib)(n) and (Aib-(S)Ant-Pro)(n) oligomers display a well-defined folded conformation featuring intramolecular mixed hydrogen bonding (7/11) and intra-residual (6/5) H-bonding interactions, respectively.

}, issn = {1359-7345}, doi = {10.1039/c3cc48850k}, author = {Kale, Sangram S. and Kunjir, Shrikant M. and Gawade, Rupesh L. and Puranik, Vedavati G. and Rajamohanan, P. R. and Sanjayan, Gangadhar J.} } @article { ISI:000337149900033, title = {Design, synthesis and cytotoxicity of novel N-benzylpiperidin-4-one oximes on human cervical cancer cells}, journal = {Journal of Chemical Sciences}, volume = {126}, number = {3}, year = {2014}, month = {MAY}, pages = {861-873}, publisher = {INDIAN ACAD SCIENCES}, type = {Article}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

A series of fifteen diversified N-benzylpiperidin-4-one oximes were synthesized and characterized by their NMR spectral data. Additionally, single-crystal XRD analysis was performed for the representative symmetrically and unsymmetrically substituted molecules. All the synthesized oximes from unsymmetrical ketones existed as E-isomer as witnessed by their NMR and XRD data. Among the synthesized target compounds that evaluated for their in vitro cytotoxicity against human cervical carcinoma (HeLa) cells, five compounds were potent with IC50 \< 17 mu M. 1-Benzyl-2,6-bis(4-isopropylphenyl)-3-methylpiperidin-4-one oxime 3c with an IC50 of 13.88 mu M was found to be the best active compound as depicted by the microscopic analysis.

}, keywords = {Cytotoxicity, HeLa cells, N-benzylpiperidin-4-one oximes, single-crystal XRD}, issn = {0974-3626}, doi = {10.1007/s12039-014-0622-z}, author = {Dindulkar, Someshwar D. and Bhatnagar, Ira and Gawade, Rupesh L. and Puranik, Vedavati G. and Kim, Se-Kwon and Anh, Dong Hyun and Parthiban, Paramasivam and Jeong, Yeon Tae} } @article { ISI:000330083100010, title = {Formation of a pseudo-beta-hairpin motif utilizing the Ant-Pro reverse turn: consequences of stereochemical reordering}, journal = {Organic \& Biomolecular Chemistry}, volume = {12}, number = {5}, year = {2014}, month = {FEB}, pages = {774-782}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Herein, we report a special case of pseudo-beta-hairpin formation by tetrapetide sequences featuring a two-membered Ant Pro dipeptide motif (Ant = anthranilic acid and Pro = proline) at the loop region. These folded structures uniquely feature the presence of C9- and C17-H-bonding patterns at reverse turn and interstrand regions, respectively. Their hairpin nucleation and folding propensities have been expounded using solution and solid state studies of distinct stereochemically altered sequences.

}, issn = {1477-0520}, doi = {10.1039/c3ob42016g}, author = {Nair, Roshna V. and Kotmale, Amol S. and Dhokale, Snehal A. and Gawade, Rupesh L. and Puranik, Vedavati G. and Rajamohanan, Pattuparambil R. and Sanjayan, Gangadhar J.} } @article { ISI:000341513700006, title = {Nucleophilic ring-opening of benzoxazinones by dbu: some observations}, journal = {Synthetic Communications}, volume = {44}, number = {20}, year = {2014}, month = {AUG}, pages = {2955-2960}, publisher = {TAYLOR \& FRANCIS INC}, address = {530 WALNUT STREET, STE 850, PHILADELPHIA, PA 19106 USA}, abstract = {

This communication demonstrates the formation of an unusual nucleophilic ring opening of benzoxazinones by 1,8-diazabicycloundec-7-ene (DBU). This observation contradicts the intrinsic feature of a hindered nonnucleophilic base like DBU. Confirmation of the product was achieved via single-crystal X-ray diffraction studies.

}, keywords = {Benzoxazinones, caprolactam, DBU, HATU}, issn = {0039-7911}, doi = {10.1080/00397911.2014.910529}, author = {Baravkar, Sachin B. and Roy, Arup and Gawade, Rupesh L. and Puranik, Vedavati G. and Sanjayan, Gangadhar J.} } @article { ISI:000332485000048, title = {Probing the folding induction ability of orthanilic acid in peptides: some observations}, journal = {RSC Advances}, volume = {4}, number = {25}, year = {2014}, month = {JAN}, pages = {13018-13025}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

This paper describes the ability of orthanilic acid (2-aminobenzenesulfonic acid, (S)Ant) to promote folding when introduced in a peptide sequence. Three peptide sequences, containing orthanilic acid (SAnt) with a sulfonamide moiety in the turn segment, have been synthesized in the solution phase using suitable coupling agents, and their structural aspects investigated using NMR and X-ray crystallographic studies. Solid- and solution-state conformational analyses reveal that the peptide sequences containing orthanilic acid in their backbone exist in a folded conformation featuring long-range 15-membered ring H-bonding.

}, issn = {2046-2069}, doi = {10.1039/c3ra47039c}, author = {Roy, Arup and Kotmale, Amol S. and Gawade, Rupesh L. and Puranik, Vedavati G. and Rajamohanan, P. R. and Sanjayan, Gangadhar J.} } @article { ISI:000365930300028, title = {Furosemide cocrystals with pyridines: an interesting case of color cocrystal polymorphism}, journal = {Crystal Growth \& Design}, volume = {15}, number = {12}, year = {2015}, month = {DEC}, pages = {5858-5872}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Furosemide (FS), a loop diuretic drug commonly used for the treatment of hypertension and edema, exhibited color cocrystal polymorphism with coformer 4,4{\textquoteright}-bipyridine (4BPY) in the stoichiometry 2:1, albeit both the API and the cocrystal former are colorless. Crystallization from ethanol, isopropanol, ethanol-water (v/v, 1/1) mixture, and acetonitrile yielded pale yellow (form II, thin needles) and orange (form 1II, blocks) cocrystals concomitantly. Needles appeared from solution within a day, while the blocks were obtained after 1-2 days from the same flask, indicating that yellow needles were formed faster and the orange blocks were perhaps formed under thermodynamic conditions. Form 1I cocrystals could also be produced from the variety of common solvents. Cocrystallization of FS with 2,2{\textquoteright}-bipyridine (2BPY) and 4-aminopyridine (4AP) gave colorless cocrystals 2 and 3, respectively, and did not exhibit polymorphism. The single-crystal X-ray structures, powder X-ray diffraction, photophysical characterization, differential scanning calorimetry, hot stage microscopy studies, and density functional theory (DFT) calculations provide insight into the structure property relationship. The common structural features observed in all of the structures is the formation of sandwich motifs comprising FS and pyridines through pi-stacking interactions. These motifs are linked differently through hydrogen bonding interactions in all three directions. The significant color difference between the two cocrystals dimorphs could be attributed to the different pi-stacking patterns and hydrogen bonding interactions between molecules of FS and 4BPY in their cocrystal structures. Investigation on the origin of the color difference using DFT calculations revealed the decrease in HOMO-LUMO gap for form 1II cocrystals (orange) compared to form 1I crystals (light yellow). The crystal-to-crystal thermal transformation of form 1I crystals to form 1II crystals of 1 suggests the role of pi-stacking assemblies in driving the self-assembly.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.5b01240}, author = {Sangtani, Ekta and Sahu, Sanjay Kumar and Thorat, Shridhar H. and Gawade, Rupesh L. and Jha, Kunal K. and Munshi, Parthapratim and Gonnade, Rajesh G.} } @article {43630, title = {3-Aminothiophenecarboxylic acid (3-Atc)-induced folding in peptides}, journal = {New Journal of Chemistry}, volume = {40}, year = {2016}, month = {SEP}, pages = {9205-9210}, abstract = {This paper describes the consequences of incorporating a constrained heterocyclic aromatic b-amino acid 3-aminothiophenecarboxylic acid (3-Atc) into peptides containing beta-turn forming elements such as Pro-Gly motif and the effect on the secondary structural architecture of the entire peptide backbone. Conformational investigations of oligomers comprising an alpha,beta,alpha peptide sequence were carried out by single-crystal X-ray diffraction, solution-state NMR, nOe-restrained MD simulation and circular dichroism studies. The results suggested that these peptide sequences assume helical architecture. The helical folding in the oligomers was found to be devoid of inter-residual H-bonding, instead found to be stabilized by a co-operative effect of 6-membered H-bonding within the 3-Atc unit and conformational restrictions of individual amino acids in the peptide backbone.}, doi = {10.1039/c6nj01667g}, author = {Ingole, Tukaram S. and Kotmale, Amol S. and Gawade, Rupesh L. and Gonnade, Rajesh G. and Rajamohanan, Pattuparambil R. and Sanjayan, Gangadhar J.} } @article { ISI:000373747700077, title = {Additive mediated syn-anti conformational tuning at nucleation to capture elusive polymorphs: remarkable role of extended pi-stacking interactions in driving the self-assembly}, journal = {Crystal Growth \& Design}, volume = {16}, number = {4}, year = {2016}, month = {APR}, pages = {2416-2428}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Understanding the process of prenucleation clustering at supersaturating stage is of significant importance to envisage the polymorphism in crystalline materials. Preferential formation of a thermodynamically stable crystal form suggests energetically favored patterns of interactions which control molecular aggregation during nucleation. Introduction of additives during crystallization is sometimes used as a suitable strategy to obtain metastable polymorphs in cases where it is not easy to capture the same by conventional crystallization methods. Comparative analysis of energy relationships and intermolecular interactions between thermodynamically stable and metastable crystal forms provides valuable clues about the nature of growth synthons at prenucleation clustering and preferential crystallization of the thermodynamic form. Conformationally flexible sulfonamide/sulfoester derivatives constituting electron rich and electron deficient aromatic rings were synthesized to study the interplay between pi-stacking and hydrogen bonding synthons. We have identified and characterized the thermodynamically stable and metastable elusive polymorphs of aromatic sulfonamides 1 and 2 and sulfoesters 3 and 4. However, these compounds eluded polymorphism during crystallisation from various common solvents/conditions and only produced thermodynamically stable crystals forms (form I crystals). Surprisingly, exploitation of pyrazinamide as an additive in different stoichiometric ratios during crystallization gave elusive polymorphs [three for 1 (form 1II, form 1III, and form 1IV) and one each for 2 (form 2II), 3 (form 3II), and 4 (form 4II)]. Molecules in stable crystal forms of these compounds are linked via extended chains of parallel displaced pi...pi stacking interactions that seem to play a vital role in driving the self-assembly of molecules and subsequently governing the nucleation process. In contrast, molecules in metastable polymorphs are devoid of such extended pi-stacking assemblies. Interestingly, differential scanning calorimetry, hot stage microscopy, and X-ray crystallographic studies confirmed the thermal crystal-to-crystal transition of all three metastable polymorphs of 1 (form 1II, form 1III, and form 1IV) to its thermodynamically stable crystal form (form 1I). Conformational analysis of molecule 1 using density functional theory calculations also validated higher stability for syn conformation (observed in Form 1I crystals) over anti and midway conformations (seen in metastable polymorphs). Melt crystallization of form 1I crystals of 1 on the larger face (001) of delta-pyrazinamide and lattice matching analysis (GRACE) revealed that the layered arrangement of molecules of delta-pyrazinamide (on 001 face) during heterogeneous nucleation acts as a template (heteroepitaxy) to provide a preferential site for the nucleation of new metastable polymorphs by selectively inhibiting the most preferred crystal form from growing into the nucleus. Solution state one- and two-dimensional (NOESY) H-1 NMR, scanning electron microscopy, and a Cambridge Structural Database survey were conducted to substantiate the role of additives during crystallization.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.6b00204}, author = {Gawade, Rupesh L. and Chakravarty, Debamitra K. and Kotmale, Amol and Sangtani, Ekta and Joshi, Pranaya V. and Ahmed, Awais and Mane, Manoj V. and Das, Susanta and Vanka, Kumar and Rajamohanan, Pattuparambil R. and Puranik, Vedavati G. and Gonnade, Rajesh G.} } @article { ISI:000368941700025, title = {Comparative study of dG affinity vs. DNA methylation modulating properties of side chain derivatives of procainamide: insight into its DNA hypomethylating effect}, journal = {RSC Advances}, volume = {6}, number = {7}, year = {2016}, month = {JAN}, pages = {5350-5358}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Procainamide derivatives have been synthesized to investigate the role of side chains in modulating the DNA methylation level in cancer cells and gain insight into its mechanism of action. The synthesized derivatives comprised of flexible (dimethyl), constrained (pyrrolidine, piperidine, morpholine) and planar aromatic (pyridine, phenyl) side chain motifs. The affinity of procainamide and its derivatives towards the deoxyguanosine (dG) base in neutral form has been assessed by performing Differential Pulse Voltammetry (DPV) under physiological conditions. Further, molecular docking with hemimethylated CpG rich DNA acquired from an active mDNMT-1-DNA (PDB ID-4DA4) crystal structure, reveals their preferential non-covalent interaction with dG nucleobase in the intercalation cavity of the minor groove. Differential affinity of the derivatives to dG base in neutral and bound forms (DNA) is correlated with their DNA methylation modulating properties at sub-lethal concentrations. Among all the derivatives, a compound with an aromatic phenyl side chain (1) has shown a highest binding affinity for dG nucleobase in neutral form as well as for partially denatured CpG rich DNA which is attributed to the formation of p/p stacking interaction in addition to N-H/O hydrogen bonding with the pyrimidine ring of dG base. It also shows the highest cytotoxicity and global hypomethylation at a sub-lethal level in the MCF-7 cancer cell line compared to other derivatives and procainamide. A docking study has also illustrated the plausible structural basis of DNA methylation modulating a property of procainamide. Strong association of procainamide with dG bases of partially denatured CpG rich DNA via H-bonding and other non-covalent interactions may alter the active topology of DNA required by the DNA-binding regulatory proteins (e. g. DNMT-1) which is validated by a DNMT-1 inhibition assay. This systematic investigation leads to a new potent alternative to procainamide being found and gives a plausible insight into the DNA hypomethylating effect of procainamide.

}, issn = {2046-2069}, doi = {10.1039/c5ra20012a}, author = {Gawade, Rupesh L. and Chakravarty, Debamitra K. and Debgupta, Joyashish and Sangtani, E. and Narwade, S. and Gonnade, Rajesh G. and Puranik, Vedavati G. and Deobagkar, D. D.} } @article { ISI:000372848000021, title = {Disruption of native beta-turns: consequence of folding competition between native and orthanilic acid proline-based pseudo beta-turn}, journal = {European Journal of Organic Chemistry}, number = {7}, year = {2016}, month = {MAR}, pages = {1380-1388}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

Five tetrapeptides comprising beta-turn-forming elements and a pseudo beta-turn (C9 H-bonding) based on an SAntPro (orthanilic acid - proline) motif were designed and synthesized. Their extensive conformational investigation by single-crystal X-ray crystallography, solution-state 2D NMR spectroscopic, and nOe-restrained MD simulation studies revealed the formation of C14 or C9 folding and disruption of the native beta-turn (C10 H-bonding) architecture. The striking difference between the psi(psi(2)) angle of {\textquoteleft}{\textquoteleft}i + 2{\textquoteright}{\textquoteright} residues of native beta-turn and designed peptides suggest that formation of the native beta-turn is not favored. The results suggest that other turn-forming motifs can dramatically modulate the stability of the native beta-turn structure.

}, keywords = {Conformation analysis, hydrogen bonds, Peptidomimetics, structure elucidation}, issn = {1434-193X}, doi = {10.1002/ejoc.201501558}, author = {Ingole, Tukaram S. and Vijayadas, Kuruppanthara N. and Chaitanya, K. N. and Kotmale, Amol S. and Gawade, Rupesh L. and Gonnade, Rajesh G. and Rajamohanan, P. R. and Sanjayan, Gangadhar J.} } @article {46344, title = {Crystal engineering for intramolecular pi-pi stacking: effect of sequential substitution of f on molecular geometry in conformationally flexible sulfonamides}, journal = {Crystal Growth \& Design}, volume = {19}, year = {2019}, month = {OCT}, pages = {5665-5678}, type = {Article}, abstract = {

A small library of ten sulfonamide derivatives comprising two aromatic rings was synthesized to investigate the effect of chronological positioning of the F-atom on the intramolecular pi-stacking assembly. The sequential positioning of F atoms was carried out on one of the aromatic rings that is linked to the sulfonamide moiety directly while the other aromatic ring (phenyl or pyridine) is linked by an ethyl spacer with the sulfonamide moiety. The ethyl spacer is provided to achieve the required flexibility so that both aromatic rings can bend to acquire syn conformation facilitated pi-stacking between electron-deficient and electron-rich aromatic rings. The idea was to study the interplay between hydrogen bonding and pi-stacking synthons in the conformationally flexible sulfonamide derivatives. The solid-state conformation of all the derivatives was investigated using the single-crystal X-ray diffraction technique. Crystal structure analysis revealed that the syn conformation was achieved only in trifluoro and pentafluoro sulfonamide derivatives with benzene substitution while in all other derivatives the molecules take either midway or anti conformations. None of the sulfonamide molecules with a pyridine moiety showed syn conformation. It could be because of the involvement of the pyridine N-atom in the hydrogen bonding dimeric synthon. The molecular conformation study in solution state using 2D NOESY and HOESY NMR experiments also substantiated syn conformation in a pentafluoro sulfonamide molecule with benzene substitution. The conformational analysis carried out employing density functional theory (DFT) calculations confirmed higher stability for the syn conformation over midway and anti orientations.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.9b00667}, author = {Shaikh, Samir R. and Gawade, Rupesh L. and Kumar, Deepak and Kotmale, Amol and Gonnade, Rajesh G. and Stuerzer, Tobias} }