Bimolendu Das - Academia.edu (original) (raw)
Papers by Bimolendu Das
![Research paper thumbnail of Intramolecular Cycloaddition Approach to Fused Pyrazoles: Access to 4,5-Dihydro-2H-pyrazolo[4,3-c]quinolines, 2,8-Dihydroindeno[2,1-c]pyrazoles, and 4,5-Dihydro-2H-benzo[e]indazoles](https://attachments.academia-assets.com/66851858/thumbnails/1.jpg)
](Synthesis
A straightforward and efficient method for the synthesis of pyrazoles fused with 1,2,3,4-tetrahyd... more A straightforward and efficient method for the synthesis of pyrazoles fused with 1,2,3,4-tetrahydroquinoline, 2,3-dihydro-1H-indene, or 1,2,3,4-tetrahydronaphthalene involves the formation of the tosylhydrazone from an aromatic substrate carrying aldehyde and acetylenic functionalities at appropriate positions, followed by base-promoted generation of the diazo compound and subsequent intramolecular 1,3-dipolar cycloaddition. A number of functional groups were found to be compatible for this reaction sequence and yields were moderate to very good (44–95%). A plausible reaction mechanism supported by DFT calculations has been provided to explain the formation of products.
Chemistry, an Asian journal, Jan 5, 2017
One of the important determinants in the efficiency of a molecular interaction is the necessity f... more One of the important determinants in the efficiency of a molecular interaction is the necessity for conformational changes in host and/or guest molecules upon binding. In small-molecule interactions with nucleic acids, conformational changes on both molecules are often involved, especially in intercalating binding. Mismatch binding ligands (MBLs) we described here consist of two heterocycles that predominantly exist in one conformation, so it is of interest to determine if such molecules can bind to any DNA and RNA structures. One molecule, 1-NHR, which predominantly exists as the unstacked conformation in aqueous solvent, has been successfully synthesized and characterized. Compound 1-NHR did not efficiently bind to GX/Y DNA and RNA sequences, but the binding pattern is different from that of authentic MBL naphthyridine carbamate dimer. In vitro selection of RNA that specifically binds to 1-NHR was performed from pre-miR-29a loop library RNA, and one RNA, to which 1-NHR bound with ...
Chemical & Engineering News
Agricultural and Food Chemistry W. O. Lundberg, executive director of Hormel Institute and profes... more Agricultural and Food Chemistry W. O. Lundberg, executive director of Hormel Institute and professor of agricultural biochemistry at University of Minnesota, succeeds C. S. Boruff of Hiram Walker & Sons as the new chairman of the Division of Agricultural and Food Chemistry. Receiving his Ph.D. W. O. Lundberg from j 0 hns Hopkins University in 1934, Lundberg is author of a book and approximately 70 other publications, including five patents. Chairman-elect is A. L. Elder, Corn Products Refining; and secretarytreasurer is F. M. Strong, University of Wisconsin. Councilors are A. F. Langlykke, E. R. Squibb, and A. L. Elder. Analytical Chemistry William G. Ratt, assistant director of the Riochemical Research Foundation of the Franklin Institute, Newark, Del., will serve as chairman of the Division of Analytical Chemistry for the year 1955. He takes office on Jan. 1. He was secretary of the division for five years. Other ACS activities have included Philadelphia Section and editor of The Catalyst. Chairmanelect is Ï. M. Kolthoff. Secretary-treasurer is R. P. Chapman. Councilor and alternate councilor are P. J. Elving and P. W. West, respectively. Biological Chemistry Jesse P. Greenstein, chief of the laboratory of biochemistry of National William G. Batt secretary of the section councilor, Cancer Institute, National Institute of Health, has been elected to serve as chairman of the Division of Biological Chemistry. He succeeds Ε. Ε. Snell of the Uni versity of Texas. Greenstein is au-J. P. Greenstein thor of approxi mately 200 publications, a book, and is credited with two patents. New chair man-elect is Otto Schales, Alton Ochsner Medical Foundation. Carl Baker, National Cancer Institute, will serve as secretary; and Robert A, Harte, Sharp and Dohme, will serve as treasurer. Members of the executive committee are Vernon Cheldelin and Sidney Fox. Carbohydrate Chemistry Carl C. Kesler, research and devel opment director of Penick & Ford, is a^^. w^. .. ..M^M.-u^™ the new chairman of the Division of Carbohydrate Chemistry. Author of a num ber of books and 50 patents in the field of carbohy drate chemistry, Kesler has been an Λ •• ^ ^-. active member of Carl C. Kesler ^ ACS locd gec _ tioB. The new chairman-elect is John C. Sowden, Washington University.
![Research paper thumbnail of One-Pot Access to Benzo[a]carbazoles via Palladium(II)-Catalyzed Hetero- and Carboannulations](https://attachments.academia-assets.com/66852187/thumbnails/1.jpg)
](The Journal of Organic Chemistry, 2016
Advanced Synthesis & Catalysis, 2015
PLOS ONE, 2015
Background Current chemotherapeutic agents based on apoptosis induction are lacking in desired ef... more Background Current chemotherapeutic agents based on apoptosis induction are lacking in desired efficacy. Therefore, there is continuous effort to bring about new dimension in control and gradual eradication of cancer by means of ever evolving therapeutic strategies. Various forms of PCD are being increasingly implicated in anti-cancer therapy and the complex interplay among them is vital for the ultimate fate of proliferating cells. We elaborated and illustrated the underlying mechanism of the most potent Andrographolide analogue (AG-4) mediated action that involved the induction of dual modes of cell death-apoptosis and autophagy in human leukemic U937 cells. Principal Findings AG-4 induced cytotoxicity was associated with redox imbalance and apoptosis which involved mitochondrial depolarisation, altered apoptotic protein expressions, activation of the caspase cascade leading to cell cycle arrest. Incubation with caspase inhibitor Z-VADfmk or Bax siRNA decreased cytotoxic efficacy of AG-4 emphasising critical roles of caspase and Bax. In addition, AG-4 induced autophagy as evident from LC3-II accumulation, increased Atg protein expressions and autophagosome formation. Pre-treatment with 3-MA or Atg 5 siRNA suppressed the cytotoxic effect of AG-4 implying the pro-death role of autophagy. Furthermore, incubation with Z-VAD-fmk or Bax siRNA subdued AG-4 induced autophagy and pre-treatment with 3-MA or Atg 5 siRNA curbed AG-4 induced apoptosisimplying that apoptosis and autophagy acted as partners in the context of AG-4 mediated PLOS ONE |
![Research paper thumbnail of ChemInform Abstract: Expedient and Rapid Synthesis of 1,2,3-Triazolo[5,1-c]morpholines Through Palladium-Copper Catalysis](https://attachments.academia-assets.com/66852191/thumbnails/1.jpg)
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Organic & Biomolecular Chemistry, 2014
The Journal of Organic Chemistry, 2012
A facile and efficient method for the synthesis of (E)-2-arylmethylidene-N-tosylindolines and (E)... more A facile and efficient method for the synthesis of (E)-2-arylmethylidene-N-tosylindolines and (E)-2-arylmethylidene-N-tosyl/nosyltetrahydroquinoline variants has been developed through palladium-catalyzed cyclocondensation of aryl iodides with readily available 1-(2-tosylaminophenyl)prop-2-yn-1-ols and their higher homologues, respectively. The proposed reaction mechanism invokes the operation of trans-aminopalladation during cyclization (5/6-exo-dig), which ensures exclusive (E)-stereochemistry in the products. The method is fast, operationally simple, totally regio- and stereoselective, and versatile enough to access a variety of 2-substituted indoles and quinolines. The reactions proceeded efficiently with a wide variety of substrates and afforded the corresponding products in moderate to excellent yields.
Bioorganic & Medicinal Chemistry Letters, 2010
A series of analogues of andrographolide, prepared through chemo-selective functionalization at C... more A series of analogues of andrographolide, prepared through chemo-selective functionalization at C14 hydroxy, have been evaluated for in vitro cytotoxicities against human leukemic cell lines. Two of the analogues (6a, 9b) exhibited significant potency. Preliminary studies on structure-activity relationship (SAR) revealed that the α-alkylidene-γ-butyrolactone moiety of andrographolide played a major role in the activity profile. The structures of the analogues were established through spectroscopic and analytical data.
The Journal of Organic Chemistry, 2009
A one-pot approach using palladium-copper as catalyst has been developed for the synthesis of mor... more A one-pot approach using palladium-copper as catalyst has been developed for the synthesis of morpholines fused with 1,2,3-triazole. Good regioselectivity, mild reaction conditions, high yields and short reaction time are the hallmarks of this method.
Synthesis
A straightforward and efficient method for the synthesis of pyrazoles fused with 1,2,3,4-tetrahyd... more A straightforward and efficient method for the synthesis of pyrazoles fused with 1,2,3,4-tetrahydroquinoline, 2,3-dihydro-1H-indene, or 1,2,3,4-tetrahydronaphthalene involves the formation of the tosylhydrazone from an aromatic substrate carrying aldehyde and acetylenic functionalities at appropriate positions, followed by base-promoted generation of the diazo compound and subsequent intramolecular 1,3-dipolar cycloaddition. A number of functional groups were found to be compatible for this reaction sequence and yields were moderate to very good (44–95%). A plausible reaction mechanism supported by DFT calculations has been provided to explain the formation of products.
Chemistry, an Asian journal, Jan 5, 2017
One of the important determinants in the efficiency of a molecular interaction is the necessity f... more One of the important determinants in the efficiency of a molecular interaction is the necessity for conformational changes in host and/or guest molecules upon binding. In small-molecule interactions with nucleic acids, conformational changes on both molecules are often involved, especially in intercalating binding. Mismatch binding ligands (MBLs) we described here consist of two heterocycles that predominantly exist in one conformation, so it is of interest to determine if such molecules can bind to any DNA and RNA structures. One molecule, 1-NHR, which predominantly exists as the unstacked conformation in aqueous solvent, has been successfully synthesized and characterized. Compound 1-NHR did not efficiently bind to GX/Y DNA and RNA sequences, but the binding pattern is different from that of authentic MBL naphthyridine carbamate dimer. In vitro selection of RNA that specifically binds to 1-NHR was performed from pre-miR-29a loop library RNA, and one RNA, to which 1-NHR bound with ...
Chemical & Engineering News
Agricultural and Food Chemistry W. O. Lundberg, executive director of Hormel Institute and profes... more Agricultural and Food Chemistry W. O. Lundberg, executive director of Hormel Institute and professor of agricultural biochemistry at University of Minnesota, succeeds C. S. Boruff of Hiram Walker & Sons as the new chairman of the Division of Agricultural and Food Chemistry. Receiving his Ph.D. W. O. Lundberg from j 0 hns Hopkins University in 1934, Lundberg is author of a book and approximately 70 other publications, including five patents. Chairman-elect is A. L. Elder, Corn Products Refining; and secretarytreasurer is F. M. Strong, University of Wisconsin. Councilors are A. F. Langlykke, E. R. Squibb, and A. L. Elder. Analytical Chemistry William G. Ratt, assistant director of the Riochemical Research Foundation of the Franklin Institute, Newark, Del., will serve as chairman of the Division of Analytical Chemistry for the year 1955. He takes office on Jan. 1. He was secretary of the division for five years. Other ACS activities have included Philadelphia Section and editor of The Catalyst. Chairmanelect is Ï. M. Kolthoff. Secretary-treasurer is R. P. Chapman. Councilor and alternate councilor are P. J. Elving and P. W. West, respectively. Biological Chemistry Jesse P. Greenstein, chief of the laboratory of biochemistry of National William G. Batt secretary of the section councilor, Cancer Institute, National Institute of Health, has been elected to serve as chairman of the Division of Biological Chemistry. He succeeds Ε. Ε. Snell of the Uni versity of Texas. Greenstein is au-J. P. Greenstein thor of approxi mately 200 publications, a book, and is credited with two patents. New chair man-elect is Otto Schales, Alton Ochsner Medical Foundation. Carl Baker, National Cancer Institute, will serve as secretary; and Robert A, Harte, Sharp and Dohme, will serve as treasurer. Members of the executive committee are Vernon Cheldelin and Sidney Fox. Carbohydrate Chemistry Carl C. Kesler, research and devel opment director of Penick & Ford, is a^^. w^. .. ..M^M.-u^™ the new chairman of the Division of Carbohydrate Chemistry. Author of a num ber of books and 50 patents in the field of carbohy drate chemistry, Kesler has been an Λ •• ^ ^-. active member of Carl C. Kesler ^ ACS locd gec _ tioB. The new chairman-elect is John C. Sowden, Washington University.
The Journal of Organic Chemistry, 2016
Advanced Synthesis & Catalysis, 2015
PLOS ONE, 2015
Background Current chemotherapeutic agents based on apoptosis induction are lacking in desired ef... more Background Current chemotherapeutic agents based on apoptosis induction are lacking in desired efficacy. Therefore, there is continuous effort to bring about new dimension in control and gradual eradication of cancer by means of ever evolving therapeutic strategies. Various forms of PCD are being increasingly implicated in anti-cancer therapy and the complex interplay among them is vital for the ultimate fate of proliferating cells. We elaborated and illustrated the underlying mechanism of the most potent Andrographolide analogue (AG-4) mediated action that involved the induction of dual modes of cell death-apoptosis and autophagy in human leukemic U937 cells. Principal Findings AG-4 induced cytotoxicity was associated with redox imbalance and apoptosis which involved mitochondrial depolarisation, altered apoptotic protein expressions, activation of the caspase cascade leading to cell cycle arrest. Incubation with caspase inhibitor Z-VADfmk or Bax siRNA decreased cytotoxic efficacy of AG-4 emphasising critical roles of caspase and Bax. In addition, AG-4 induced autophagy as evident from LC3-II accumulation, increased Atg protein expressions and autophagosome formation. Pre-treatment with 3-MA or Atg 5 siRNA suppressed the cytotoxic effect of AG-4 implying the pro-death role of autophagy. Furthermore, incubation with Z-VAD-fmk or Bax siRNA subdued AG-4 induced autophagy and pre-treatment with 3-MA or Atg 5 siRNA curbed AG-4 induced apoptosisimplying that apoptosis and autophagy acted as partners in the context of AG-4 mediated PLOS ONE |
Organic & Biomolecular Chemistry, 2014
The Journal of Organic Chemistry, 2012
A facile and efficient method for the synthesis of (E)-2-arylmethylidene-N-tosylindolines and (E)... more A facile and efficient method for the synthesis of (E)-2-arylmethylidene-N-tosylindolines and (E)-2-arylmethylidene-N-tosyl/nosyltetrahydroquinoline variants has been developed through palladium-catalyzed cyclocondensation of aryl iodides with readily available 1-(2-tosylaminophenyl)prop-2-yn-1-ols and their higher homologues, respectively. The proposed reaction mechanism invokes the operation of trans-aminopalladation during cyclization (5/6-exo-dig), which ensures exclusive (E)-stereochemistry in the products. The method is fast, operationally simple, totally regio- and stereoselective, and versatile enough to access a variety of 2-substituted indoles and quinolines. The reactions proceeded efficiently with a wide variety of substrates and afforded the corresponding products in moderate to excellent yields.
Bioorganic & Medicinal Chemistry Letters, 2010
A series of analogues of andrographolide, prepared through chemo-selective functionalization at C... more A series of analogues of andrographolide, prepared through chemo-selective functionalization at C14 hydroxy, have been evaluated for in vitro cytotoxicities against human leukemic cell lines. Two of the analogues (6a, 9b) exhibited significant potency. Preliminary studies on structure-activity relationship (SAR) revealed that the α-alkylidene-γ-butyrolactone moiety of andrographolide played a major role in the activity profile. The structures of the analogues were established through spectroscopic and analytical data.
The Journal of Organic Chemistry, 2009
A one-pot approach using palladium-copper as catalyst has been developed for the synthesis of mor... more A one-pot approach using palladium-copper as catalyst has been developed for the synthesis of morpholines fused with 1,2,3-triazole. Good regioselectivity, mild reaction conditions, high yields and short reaction time are the hallmarks of this method.