Browsing by Author "Harish K. Indurthi"

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7-Azaspiroketal as a unique and effective auxochrome moiety: demonstration in a fluorescent coumarin dye and application in cell imaging
(Royal Society of Chemistry, 2023) Harish K. Indurthi; Pooja Goswami; Samarpita Das; Pallavi Saha; Biplob Koch; Deepak K. Sharma
Replacement of electron-donating N,N-dialkyl groups with azacyclic groups has been described as a promising auxochrome to improve the low fluorescent quantum yields (ΦF) of conventional fluorophores. However, the insufficient brightness and poor solubility of fluorophores pose a significant bottleneck for bioimaging. A new type of fluorescent coumarin dye was designed and synthesized using 7-azaspiroketals as the electron-donating auxochrome group. Such modifications resulted in high-quality coumarin fluorophores with improved solubility and brightness. To the best of our knowledge, this is the first report of using apex-N-substituted azaspiroketals as an electron donor group in any class of donor-acceptor dye. Furthermore, the successful application of these new dyes in biological imaging for living cells has been demonstrated. © 2023 The Royal Society of Chemistry.
Azaspiroketal as Novel Auxochrome for Enhancing the Fluorescence Brightness and Solubility of Naphthalimide and Nitrobenzoxadiazole Dyes
(John Wiley and Sons Inc, 2024) Harish K. Indurthi; Pooja Goswami; Samarpita Das; Pallavi Saha; Biplob Koch; Deepak K. Sharma
The majority of fluorescence imaging techniques make considerable use of fluorescent dyes. Nevertheless, many structural modification techniques currently in use could not adjust the fluorophores′ properties (such as brightness, photostability, water solubility, and permeability). Herein, we report azaspiroketal-based auxochrome on naphthalimide and nitrobenzoxadiazole dyes. Their photophysical parameters revealed higher brightness and solubility than their azetidine counterparts in aqueous solution. Computational experiments were performed to study the electronic effect of azetidine and azaspiroketal on both dyes. Cytotoxicity assay indicated that azaspiroketal-based fluorophores are safe to use for their biological application. The photobleaching studies and successful application of new dyes in bioimaging were demonstrated in MDA-MB-231 cell lines. © 2024 Wiley-VCH GmbH.
Improving the fluorescence brightness of naphthalimide and nitrobenzoxadiazole dyes with cycloalkylamine auxochromes
(Elsevier Ltd, 2024) Samarpita Das; Pooja Goswami; Harish K. Indurthi; Biplob Koch; Deepak K. Sharma
We have installed cycloalkylamino auxochromes on naphthalimide (5a-5e) and nitrobenzoxadiazole (6a-6e) dyes. Their photophysical characterization revealed that the cyclobutylamino auxochrome in both dyes (5b and 6b) demonstrated high quantum yield and fluorescence brightness compared to their azetidine counterparts (5 and 6) in aqueous solution. The computational studies were performed to substantiate the experimental photophysical results. Cytotoxicity assay in breast adenocarcinoma (MDA-MB-231) and non-cancerous human embryonic kidney 293 (HEK-293) cells indicated significant biocompatibility of cyclobutylamino auxochrome. Moreover, cellular imaging and photostability experiments demonstrated the practical application of cycloalkylamino auxochromes. © 2024 Elsevier Ltd
Rapid access to 7-substituted cycloalkylamino and alkylamino analogues of 4-methylcoumarin reveals surprising emitters
(Elsevier Ltd, 2023) Samarpita Das; Pooja Goswami; Vivek K. Verma; Harish K. Indurthi; Manoj Kumar; Biplob Koch; Deepak K. Sharma
Replacement of electron-donatingN,N-dialkyl groups with four-membered azetidine has recently been used as a promising approach to improve low fluorescent quantum yields of coumarin. Herein, we report the synthesis of 7-cycloalkylamino/alkyl amino analogues (6–19) from 4-methyl umbelliferone-derived nonaflate (1a’) using Buchwald-Hartwig amination and comparison of their fluorescence activity with 7-azetidinyl-4-methylcoumarin (4). The absolute quantum yields of cyclobutylamine (7), cyclopentylamine (8), propylamine (10), butylamine (11), isopropylamine (16), and isobutylamine (17) were found to be comparable to that of the azetidine (4) coumarin. Further, the dyes were found to be biocompatible in cell lines. Also, the successful application of these new dyes in biological imaging for living cells has been demonstrated. © 2023 Elsevier Ltd
Recent trends of chromene syntheses
(Bentham Science Publishers, 2023) Samarpita Das; Pulkit Asati; Harish K. Indurthi; Ashutosh Kumar Dash; Deepak K. Sharma
2H/4H-chromenes (2H/4H-Ch) structural scaffolds have been widely employed in the synthesis of many natural products and medicinal agents. 2H/4H-Ch have attracted considerable attention due to their various pharmacological activities, such as anticonvulsant, anticholinesterase, anticancer, anti-tuberculosis, antimicrobial, and inhibitory activity against monoamine oxidase (MAO), and anti-diabetic activities. In literature, the synthesis of 4H-chromenes was performed by one-pot Knoevenagel condensation of resorcinol, aryl aldehydes, and malononitrile in the presence of basic catalysts. Also, 2H-Ch analogs were performed by the Wittig-Horner-Emmons and Suzuki-Miyaura cross-coupling reactions. A description of recent advances in the syntheses of chromenes is presented in this chapter. The strategies for the synthesis of 2H/4H-Ch discussed in this chapter are organocatalysts, organometallic or metal catalysts, heterogeneous base catalysts, enzymatic catalysts, and green chemistry-based approaches. © 2023 Bentham Science Publishers. All rights reserved.