Indian Journal of Chemistry

Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical

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CODEN: ICACEC; ISSN: 0376-4710 (Print), 0975-0975 (Online)

 

Special Issue on Complex Chemical Systems

 

 

VOLUME 52A

NUMBER 8-9

AUG-SEPT 2013

CONTENTS

Advances in Contemporary Research

 

973

 

Site-specific chemical modifications of proteins

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Divya Agrawal* & Christian P R Hackenberger*

 

 

 

An overview of the chemical and biochemical approaches to functionalize peptides and proteins with the desired molecular components is presented. Site-directed methods to incorporate unnatural groups into biomolecules and the development of bioorthogonal transformations involving unnatural functional groups have been reviewed.

 

 

 

992

 

Organometallic complexes: Catalysis and application in protein modification

 

 

 

 

 

 

 

 

 

 

 

 

Maheshwerreddy Chilamari & Vishal Rai*

 

 

 

Organometallic catalysis has witnessed phenomenal growth with time, and methodologies have been developed to facilitate a variety of chemo-, regio- and stereoselective reactions. The potential of these transformations has been examined to differentiate the reactivity of amino acid residues in a peptide or protein. The efforts en route to develop new catalytic approaches in this area have been delineated in this review.

 

 

 

 

Papers

 

1004

 

Synthesis and fluorescence properties of a full set of extended RNA base analogues

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pramod M Sabale, Ashok Nuthanakanti &
Seergazhi G Srivatsan
*

 

 

 

Synthesis and fluorescence properties of a full set of environment-sensitive RNA base analogues derived by conjugating benzofuran moiety at the 5- and 8-positions of pyrimidine and purine bases, respectively, are described.

 

 

 

1014

 

Rapid synthetic access to caged RNA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Alexandre Rodrigues-Correia, Tatjana Stoess,
Julia Wilhelm, Beata Berlin & Alexander Heckel
*

 

 

 

Novel caged RNA is synthesized using a convertible nucleoside approach. The ability of the resulting sequences to destabilize duplex structures is compared.

 

 

1019

 

Synthetic glutathione peroxidase mimics: Effect of nucleophilicity of the aryl thiol cofactor on the antioxidant activity

 

 

 

 

 

 

 

Krishna Pada Bhabak, Debasish Bhowmick & Govindasamy Mugesh*

 

 

 

 

 

1026

 

Fabrication of biotin functionalised SiO2 EM grid for studying biotin tagged biomolecules

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Indrani Chakraborty, Abhijit Saha & Surajit Ghosh*

 

 

 

Biotinylated SiO2 EM grid is fabricated through covalent chemical functionalisation for studying biotin/avidin tagged-biomolecular interaction under electron microscope.

 

 

 

1031

 

Effect of β-CD on refolding dynamics of the unfolded and reduced states of human serum albumin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Uttam Anand, Subhadip Ghosh, Nirmal Kumar Das, Narayani Ghosh, Ramakanta Mondal,
Arshad
Karumbamkandathil &
Saptarshi Mukherjee
*

 

 

 

The behavior of the unfolded and reduced states of HSA is different towards the addition of β-CD; the former can be refolded whereas the latter cannot.

 

 

 

1041

 

Coordination site discrimination in substituted  bioessential purine ligands

 

 

 

 

 

 

 

 

 

 

 

Ashutosh Kumar Mishra, Rajneesh Kumar Prajapati & Sandeep Verma*

 

 

 

 

 

 

 

1047

 

Effect of room temperature ionic liquids on femtosecond solvation dynamics in a triblock copolymer (P123) gel

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Amit Kumar Mandal, Shirsendu Ghosh,
Tridib Mondal, Atanu Kumar Das &
Kankan Bhattacharyya
*

 

 

 

 

 

 

1056

 

Behavior of water dimer under the influence of external electric fields

 

 

 

 

 

 

 

 

 

 

 

 

Arobendo Mondal, H Seenivasan, Sameer Saurav & Ashwani K Tiwari*

 

 

 

 

 

 

 

1061

 

Density functional theory study of oxygen clathrate hydrates

 

 

 

 

 

 

 

 

 

 

 

K R Ramya & Arun Venkatnathan*

 

 

 

 

 

 

1066

 

Organostannoxane-supported Pd(0) nanoparticles as
an efficient catalytic system for alkyne dimerization

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Vadapalli Chandrasekhar* &
Ramakirushnan Suriya Narayanan

 

 

 

Phosphine appended organostannoxane supported palladium nanoparticles are utilized as a reusable catalytic system for the homo-coupling of terminal alkynes.

 

Created with GIMP

 

 

 

1072

 

Ferrocene-appended anionic N-heterocyclic carbene and its complex with silver(I): Synthesis, structure and catalytic evaluation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Abir Sarbajna, Nabanita Sadhukhan, Sayantani Saha & Jitendra K Bera*

 

 

 

 

 

 

1078

 

Synthesis, characterization and crystal structure
of 2-((4-bromophenyl) carbamoyl) phenylselenenyl bromide derived from oxidative addition of
bromine to 2-phenyl-1,2-benzoisoselenazol-3-(2H)-one

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Shah Jaimin Balkrishna, Amit Kumar, Piyush Panini, Shailesh Kumar & Sangit Kumar*

 

 

 

 

 

1086

 

Base mediated 5-endo-dig cyclization of N-propargyl proline derivatives: A facile entry to pyrrolizidine scaffolds

 

 

 

 

 

 

 

 

Sriram Mahesh, Manish Pareek,
B T Ramanjaneyulu, Gurpreet Kaur &
R Vijaya Anand
*

 

 

 

An efficacious and metal-free protocol for the construction of pyrrolizidine core from N-propargyl proline derivatives is described.

 

Graphical abstract.tif

 

 

1093

 

Expeditious approach to the Amarylidaceae alkaloids, crinasiadine and its analogues, via a palladium-catalyzed intramolecular direct C-H arylation

 

 

 

 

 

 

 

 

 

 

 

Sourabh Mishra, Subhadip De, Badrinath N Kakde, Dhananjay Dey & Alakesh Bisai*

 

 

 

 

 

1103

 

One-step synthesis of 3-formyl-2-furylcarbinols and elaboration to unprecedented furotropones

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Seema Dhiman & S S V Ramasastry*

 

 

 

Graphilcal abstract.tif

 

 

 

1113

 

Diastereoselective construction of a new class of nicotine analogues having contiguous stereocenters via 1,3- dipolar cycloaddition of azomethine ylides

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Vadla Rajkumar & Srinivasarao Arulananda Babu*

 

 

 

Diastereoselective synthesis of a new class of nicotine derivatives is accomplished through azomethine ylide cycloaddition.

 

 

Authors for correspondence are indicated by (*)

 

 

 

 

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 973-991

 

 

 

Site-specific chemical modifications of proteins

Divya Agrawala, * & Christian P R Hackenbergera, b, *

aLeibniz-Institut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str- 10, 13125, Berlin, Germany

bHumboldt Universität zu Berlin, Institut für Organische und Bioorganische Chemie,
Institut für Chemie, Brook-Taylor-Str. 2, 12489 Berlin, Germany

Email: agrawal@fmp-berlin.de (DA); hackenbe@fmp-berlin.de (CPRH)

Received 8 April 2013; accepted 10 May 2013

Since long, peptides and proteins have been recognized as targets for the development of synthetic methodologies. There have been major advances in the development of methods for the site-specific modifications. The naturally occurring functionalities in peptides and proteins are used to modify the less common amino acid targets. The most important benefit of chemical bioconjugation techniques using naturally occurring amino acids is that they do not require additional biochemical techniques to install unnatural functionalities for chemoselective reactions. However, unnatural functionalities can well be incorporated into peptides and proteins followed by the establishment of bioorthogonal coupling methodologies. The unnatural amino acids can be incorporated into proteins either in a site-directed or residue-specific fashion. Bioorthogonal chemistry is an important tool for the development of synthetic methodologies and for further advances in biological research. A variety of methods exist that tag cellular components with reporters not only for visualization but also for isolation from biological samples. In this review, we present an overview of the efforts of both chemical and biochemical approaches to functionalize peptides and proteins with the desired molecular components. We focus on the site-directed methods to incorporate unnatural groups into biomolecules and the development of bioorthogonal transformations involving unnatural functional groups.

Keywords: Protein modifications, Site-selective modifications, Protein functionalities, Bioorthogonal transformations, Chemoselective reactions, Bioconjugation, Chemical bioconjugation, Copper catalysed reactions, Biomolecules, Amino acids, Unnatural amino acids, Canonical amino acids, Azides, Alkynes, Ketones, Aldehydes

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 992-1003

 

 

Organometallic complexes: Catalysis and application in
protein modification

Maheshwerreddy Chilamari & Vishal Rai*

Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal 462 023, MP, India

Email: vrai@iiserb.ac.in

Received 31 March 2013; accepted 16 May 2013

Organometallic catalysis has witnessed phenomenal growth with time and methodologies have been developed to facilitate a variety of chemo-, regio- and stereoselective reactions. The potential of these transformations has been examined to differentiate the reactivity of amino acid residues in a peptide or protein in recent years. However, these biomacromolecules extend astringent chemoselectivity challenge to the classical methodologies. The efforts en route to develop new catalytic approaches in this area has been delineated in this review.

Keywords: Organometallic catalysis, Metallopeptides, Peptide-peptide interactions, Protein-protein interactions, Post-translational protein modification

 

Papers

 

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1004-1013

 

 

Synthesis and fluorescence properties of a full set of
extended RNA base analogues

Pramod M Sabale, Ashok Nuthanakanti & Seergazhi G Srivatsan*

Indian Institute of Science Education and Research, 900, NCL Innovation Park,
Dr Homi Bhabha Road, Pune 411 008, India

Email: srivatsan@iiserpune.ac.in

Received 5 April 2013; revised and accepted 13 April 2013

The synthesis and photophysical characterization of a complete set of fluorescent RNA base analogues derived by conjugating benzofuran moiety at the 5- and 8-positions of pyrimidine and purine bases, respectively, are described. Benzofuran-modified pyrimidine and purine ribonucleoside analogues exhibit contrasting fluorescence properties. Pyrimidine analogues are moderately emissive with emission maximum in the visible region, and importantly, are highly sensitive to solvent polarity and viscosity changes. On the other hand, purine analogues are highly emissive and are minimally affected by solvation and viscosity effects. Thorough photophysical analysis reveals that the pyrimidine and purine ribonucleosides displaying distinct and probe-like fluorescence properties could be useful in designing nucleic acid based biophysical tools to study nucleic acid structure and function.

Keywords: Fluorescence spectroscopy, Fluorescence probes, Ribonucleoside analogues, Environment sensitive   probes, Nucleic acids

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1014-1018

 

 

Rapid synthetic access to caged RNA

Alexandre Rodrigues-Correia, Tatjana Stoess, Julia Wilhelm, Beata Berlin & Alexander Heckel*

Goethe University Frankfurt, Institute for Organic Chemistry and Chemical Biology,
Buchmann Institute for Molecular Life Sciences, Max-von-Laue-Str. 9, 60438 Frankfurt (M), Germany

Email: heckel@uni-frankfurt.de

Received 19 March 2013; accepted 30 April 2013

Light-activatable RNA with “caged” nucleobases is a versatile tool for light-control of RNA interference, riboswitch folding or miRNA or ribozyme action. Till date the respective caged and protected phosphoramidites for the solid-phase RNA synthesis are obtained in lengthy syntheses. Herein we explore the use of convertible nucleoside residues for a rapid access to nucleobase-caged RNA. In these studies we have also prepared the first RNA with a caging group on an N2-position of a guanosine. The obtained caged sequences are compared in their duplex destabilizing ability via melting temperature measurements.

Keywords: RNA, Caged RNA, Light-activatable RNA, Duplex destabilizing

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1019-1025

 

 

Synthetic glutathione peroxidase mimics: Effect of nucleophilicity of the
aryl thiol cofactor on the antioxidant activity

Krishna Pada Bhabak, Debasish Bhowmick & Govindasamy Mugesh*

Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore, 560 012, India

Email: mugesh@ipc.iisc.ernet.in

Received 14 March 2013; accepted 30 April 2013

Catalytic activity of a series of potent amide- and amine-based organoselenium compounds are studied in the presence of various aromatic thiols having electron donating and electron withdrawing substituents on the phenyl ring. This study suggests that the antioxidant activities of the synthetic GPx mimics can be significantly increased by the incorporation of a suitable electron donating group on the phenyl ring of an aromatic thiol.

Keywords: Glutathione peroxidase, Antioxidants, Organoselenium compounds, Aromatic thiols, Peroxide reduction, Thiols, Enzymatic activity, Enzyme mimics

 

Indian Journal of Chemistry

Vol. 52 A, Aug-Sept 2013, pp. 1026-1030

 

 

Fabrication of biotin functionalised SiO2 EM grid for studying
biotin tagged biomolecules

Indrani Chakraborty, Abhijit Saha & Surajit Ghosh*

Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4 Raja S C Mullick Road,
Jadavpur, Kolkata 700 032, West Bengal, India

Email: sghosh@iicb.res.in

Received 23 March 2013; accepted 10 May 2013

A biotin functionalised SiO2 electron microscope grid has been developed for studying various biotin/avidin tagged biomolecules onto the grid surface under electron microscope. As an application, we have shown successful immobilisation of streptavidin gold nanoparticles and biotinylated microtubules through biotin-streptavidin-biotin interaction. This grid will be useful for studying the structures of various biotin-tagged proteins and their complexes under electron microscope.

Keywords: Electron microscopy, Surface functionalisation, Silica EM grid, Gold nanoparticles, Nanoparticles, Microtubules, Biotin

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1031-1040

 

 

Effect of β-CD on refolding dynamics of the unfolded and
reduced states of human serum albumin

Uttam Anand, Subhadip Ghosh, Nirmal Kumar Das, Narayani Ghosh, Ramakanta Mondal,
Arshad Karumbamkandathil & Saptarshi Mukherjee*

Department of Chemistry, Indian Institute of Science Education and Research Bhopal,
ITI Campus (Gas Rahat) Building, Govindpura, Bhopal 462 023, Madhya Pradesh, India

Email: saptarshi@iiserb.ac.in

Received 13 March 2013; revised and accepted 27 May 2013

The anionic surfactant, sodium dodecyl sulfate (SDS), unfolds the circulatory protein human serum albumin (HSA) and binds to it in three distinct stages. The structural integrity rendered by the seventeen disulfide bridges inherently present in HSA, does not make the protein behave as an extended polymer upon SDS treatment. However, when this unfolded protein is subjected to β-cyclodextrin (β-CD), it regains back a substantial portion of its secondary structure. The behavior of the reduced state of the protein, which was achieved by treatment with dithiothretol, is totally different from that of the unfolded state; on addition of β-CD to this reduced state, the protein loses its structure further. Using steady-state and time-resolved spectroscopic analyses, these unfolded and reduced states of the protein, when subjected to β-CD, have been characterized. The mechanism of refolding of the unfolded state has been ascribed to the removal of the bound SDS molecules by β-CD and the reversible unfolding and refolding pathways.

Keywords: Protein unfolding, Protein refolding, Refolding dynamics, Fluorescence, Steady-state spectroscopy,
Time-resolved spectroscopy, Disulfide bridges, Sodium dodecyl sulfate, Cyclodextrins

 

Indian Journal of Chemistry

Vol. 52 A, Aug-Sept 2013, pp. 1041-1046

 

 

Coordination site discrimination in substituted bioessential purine ligands

Ashutosh Kumar Mishra, Rajneesh Kumar Prajapati & Sandeep Verma*

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016 (UP), India

Received 13 May 2013; revised and accepted 5 June 2013

Email: sverma@iitk.ac.in

The synthesis and crystallographic investigations of N6 and/or N9 substituted adenine analogues with coinage metal ions are described. While N6 disubstitution in an N9-unsubstituted adenine unit results in N3,N9-bidentate coordination mode resulting in a dinuclear motif, further substitution at N9 position directs the incoming metal to get coordinated at N3 position. However, N6,N9-monosubstituted adenine derivative, which relieves some steric hindrance at N6, allows for N7 coordination of copper ions.

Keywords: Coordination chemistry, Metal-nucleobase frameworks, Adenine analogues, Purine ligands, Transition metals, Coinage metals, Silver, Copper

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1047-1055

 

 

Effect of room temperature ionic liquids on femtosecond solvation
dynamics in a triblock copolymer (P123) gel

Amit Kumar Mandal, Shirsendu Ghosh, Tridib Mondal, Atanu Kumar Das & Kankan Bhattacharyya*

Physical Chemistry Department, Indian Association for the Cultivation of Science,
Jadavpur, Kolkata 700 032, India

Email: pckb@iacs.res.in

Received 27 January 2013; revised and accepted 9 May 2013

Effect of two room temperature ionic liquids (RTIL, [pmim][Br] and [pmim][BF4]) on the solvation dynamics and anisotropy decay of coumarin 480 (C480) in P123 gel has been studied using femtosecond up-conversion. In P123 gel, C480 displays a significant excitation wavelength dependence of emission maximum (red edge excitation shift, REES of 18 nm) and solvation dynamics, which suggest heterogeneous structure of the P123 gel. Dynamics of different regions of the P123 gel-RTIL is probed by the variation of excitation wavelength (lex). For lex = 435 nm, the polar peripheral region of the P123-RTIL gel is preferentially excited with a very small contribution of the non-polar region. At lex = 375 nm, contribution of the non-polar region is very large. The solvation dynamics in both the core and corona regions of P123 gel-RTIL is faster than that in P123 gel. The anisotropy decay of C480 in the P123 gel-RTIL phase is about two times faster as compared to P123 gel. The results are compared with a recent fluorescence correlation spectroscopic study on diffusion in RTIL-P123 gel.

Keywords: Ionic liquids, Solvation dynamics, Fluorescence spectroscopy, Anisotropy decay, Copolymers,
Triblock copolymers

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1056-1060

 

 

Behavior of water dimer under the influence of external electric fields

Arobendo Mondal, H Seenivasan, Sameer Saurav & Ashwani K Tiwari*

Department of Chemical Sciences, Indian Institute of Science Education and Research, Kolkata,
Mohanpur Campus, Krishivisyavidyalaya PO, Nadia, 741 252 West Bengal, India

Email: ashwani@iiserkol.ac.in

Received 3 April 2013; accepted 29 April 2013

A detailed quantum chemical study has been carried out at the CCSD(T) level of theory to understand the behavior of water dimer under the influence of external electric fields. The energy values obtained at this level of theory follow the same trend as observed with the DFT and MP2 levels of theory. Our calculations show that water dimer gets stabilized with increase in the strength of electric field. A slight increase in the hydrogen bond distance and relatively larger decrease in the hydrogen bond angle is found with the increase in the strength of electric field. The dipole moment and HOMO-LUMO energy gap increase with the increase in the strength of electric field.

Keywords: Water dimer, Electric field, Coupled cluster methods, Dipole moments, HOMO-LUMO energy gap

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1061-1065

 

 

Density functional theory study of oxygen clathrate hydrates

K R Ramya & Arun Venkatnathan*

Department of Chemistry, Indian Institute of Science Education and Research, Pune, 411 008, India

Email: arun@iiserpune.ac.in

Received 10 April 2013; accepted 21 May 2013

Interaction energy and vibrational Raman spectra associated with the occupancy of oxygen molecules in dodecahedron (512) and hexakaidecahedron (51264) water cages of the sII hydrate lattice have been studied. The interaction energy shows the 512(O2) and 51264(O2)2 cages to be most stable. The spectral properties validate the most stable occupancy as observed from the interaction energy and show the following trends: The vibrational modes of water molecules in the 512(O2) cage are red shifted relative to the 512 cage, whereas, the modes in the 512(O2)2 cage are blue shifted relative to the 512(O2) cage. The vibrational modes of water molecules in the 51264(O2) and 51264(O2)2 cages show a red shift relative to the 51264 and 51264(O2) cages respectively, although the modes in the 51264(O2)3 cage is blue shifted relative to the 51264(O2)2 cage.

Keywords: Density functional calculations, Oxygen clathrate hydrates, Cage compounds, Interaction energy, Vibrational spectroscopy, Raman spectra, sII hydrate lattice

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1066-1071

 

 

Organostannoxane-supported Pd(0) nanoparticles as an efficient
catalytic system for alkyne dimerization

Vadapalli Chandrasekhar* & Ramakirushnan Suriya Narayanan

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India

Email: vc@iitk.ac.in

Received 10 April 2013; accepted 14 May 2013

An organostannoxane cage, [n-BuSn(O)OC(O)R]6 [R = -C6H4-p-PPh2] (SnP), has been utilised to stabilise
palladium(0) nanoparticles (SnPPd). The latter is shown to efficiently catalyse the alkyne dimerisation reactions under mild reaction conditions.

Keywords: Organostannoxane, Cage molecules, Catalysis, Alkyne dimerization, Nanoparticles, Palladium, Tin

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1072-1077

 

 

Ferrocene-appended anionic N-heterocyclic carbene and its complex with silver(I): Synthesis, structure and catalytic evaluation

Abir Sarbajna, Nabanita Sadhukhan, Sayantani Saha & Jitendra K Bera*

Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India

Email: jbera@iitk.ac.in

Received 10 April 2013; accepted 14 May 2013

A binuclear Ag(I) complex (1) bridged by two anionic N-heterocyclic carbene (NHC) ligands ferrocenoyl(1-mesityl-imidazol-2-ylidine-3-yl)amide is synthesized. X-ray structure reveals a [Ag···Ag] core spanned by two ligands, each bridging two metals through carbene carbon and amido nitrogen. The neutral complex (1) is highly soluble in a variety of organic solvents and is thermally stable. Complex (1) efficiently catalyses aniline-mediated synthesis of substituted quinolines from 2-aminobenzaldehyde and terminal alkynes.

Keywords: Carbenes, N-Heterocyclic carbenes, Silver, Bimetallic catalysis, Quinolines, Hydroamination

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1078-1085

 

 

Synthesis, characterization and crystal structure of
2-((4-bromophenyl) carbamoyl) phenylselenenyl bromide derived from
oxidative addition of bromine to 2-phenyl-1,2-benzoisoselenazol-3-(2H)-one

Shah Jaimin Balkrishna, Amit Kumar, Piyush Panini, Shailesh Kumar & Sangit Kumar*

Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal,
Bhopal 462 023, Madhya Pradesh, India

Email: sangitkumar@iiserb.ac.in

Received 13 March 2013; revised and accepted 22 May 2013

Oxidative addition of elemental bromine to 2-phenyl-1, 2-benzoisoselenazol-3-(2H)-one has been studied. Reaction of bromine with selenazolone gives the corresponding 2-phenyl-1,2-benzoisoselenazol-3-(2H)-one(IV) dibromide, which slowly rearranges to 2-((4-bromophenyl)carbamoyl)phenylselenenyl bromide when kept for crystallization for a longer period of time (24 days). Molecular conformation of the selenenyl bromide is found to be stabilized due to the presence of an intramolecular Se…O interaction along with the weak C-H…O and C-H…Br hydrogen bonds. The nature of the intramolecular Se…O interaction in selenenyl bromide has been studied by multi-nuclear

(1H, 13C, and 77Se) NMR spectroscopy.

Keywords: Bromination, Organoselenium compounds, X-ray diffraction, Ebselen, Selenenyl bromide

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1086-1092

 

 

Base mediated 5-endo-dig cyclization of N-propargyl proline derivatives:
A facile entry to pyrrolizidine scaffolds

Sriram Mahesh, Manish Pareek, B T Ramanjaneyulu, Gurpreet Kaur & R Vijaya Anand*

Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81,
SAS Nagar, Mohali, Punjab 140 306, India

Email: rvijayan@iisermohali.ac.in

Received 16 April 2013; revised and accepted 18 June 2013

A simple, base facilitated 5-endo-dig cyclization strategy has been exploited for the assembly of bicyclic core of pyrrolizidine alkaloids. This unprecedented protocol allows access to a diverse range of alkyl and aryl substituted pyrrolizidine scaffolds in moderate yields from readily available N-propargyl-L-proline ester derivatives under mild conditions. No catalyst or alkyne activator is required to effect this atom economical transformation.

Keywords: Bicyclic compounds, Cyclization, 5-endo-dig cyclization, Pyrrolizidine core, Propargyl amines

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1093-1102

 

 

Expeditious approach to the Amarylidaceae alkaloids, crinasiadine and its analogues, via a palladium-catalyzed intramolecular direct C-H arylation

Sourabh Mishra, Subhadip De, Badrinath N Kakde, Dhananjay Dey & Alakesh Bisai*

Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, MP 462 023, India

Email: alakesh@iiserb.ac.in

Received 27 March 2013, accepted 21 May 2013

A simple and efficient approach to the core skeleton of various Amaryllidaceae alkaloids such as phenanthridones, phenanthridines and 5, 6-dihydrophenanthridines has been achieved. The methodology involves a palladium catalyzed direct biaryl-coupling of 2-halobenzoylamines/2-halobenzylamine derivatives.

Keywords: Catalysis, Biaryl-coupling, Palladium, Alkaloids, Arylation, Crinasiadine, Phenanthridone, Phenanthridine, Dihydrophenanthridine

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1103-1112

 

 

One-step synthesis of 3-formyl-2-furylcarbinols and elaboration to

unprecedented furotropones

Seema Dhiman & S S V Ramasastry*

Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali,
Sector 81, SAS Nagar, Manuali PO, Punjab 140 306, India

 

Email: ramsastry@iisermohali.ac.in

 

Received 15 April 2013; revised and accepted 19 May 2013

 

A general and unprecedented strategy for the synthesis of furo[2,3-d]tropone system via regioselective directed

a-lithiation-alkylation and serendipitous base-promoted cyclization reaction, as key steps, has been developed. Directed

a-lithiation of furan/thiophene-3-carboxaldehydes in their masked form and subsequent reaction with aldehydes efficiently

provided in one-step, access to 3-formyl-2-furyl/thiophenylcarbinols, which are otherwise only accessible with difficulty.

The 3-formyl-2-furylcarbinols are further elaborated to the synthesis of furo[2,3-d]tropones (also known as cyclohepta[b]furan-6-ones or furotropones) in good yields via sequential bismuth(III)chloride-catalyzed furfurylation and a novel base promoted cyclization reaction. This paper describes the general approach to the synthesis of

3-formyl-2-furylcarbinols and furotropones which could find potential applications in the synthesis of several bioactive

natural products and pharmaceutics.

 

Keywords: Furfuryl alcohols, 3-Furancarboxaldehydes, 3-Formyl-2-furylcarbinols, Furotropone, Cyclohepta[b]furans, Bismuth chloride, Lithiation, Alkylation, Cyclization

 

Indian Journal of Chemistry

Vol. 52A, Aug-Sept 2013, pp. 1113-1127

 

 

Diastereoselective construction of a new class of nicotine analogues having contiguous stereocenters via 1,3- dipolar cycloaddition of azomethine ylides

Vadla Rajkumar & Srinivasarao Arulananda Babu*

Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City,
Sector 81, SAS Nagar, Mohali, Manauli PO, Punjab, 140306, India

Email: sababu@iisermohali.ac.in

Received 5 April 2013; revised and accepted 4 June 2013

Diastereoselective synthesis of several nicotine analogues via the intermolecular cycloaddition of azomethine ylides derived from the condensation reaction of nicotinaldehyde/ picolinaldehyde/ isonicotinaldehyde and
N-methyl glycine/N-benzyl glycine hydrochloride with several readily available electron-deficient 2π components, (maleimides, dialkyl fumarates, dialkyl maleates and fumaronitrile) is reported. The assembling of a new class of nicotine analogues/ functionalized 2-pyridylpyrrolidine derivatives having contiguous stereocenters has been accomplished. The stereochemistry of the representative products is unequivocally established from the single crystal X-ray structure analyses.

Keywords: Pyridine alkaloids, Azomethine ylide, 1,3-Dipolar cycloaddition, Stereoselective synthesis, Nicotine