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RESEARCH

Expanding the Genetic Alphabets	Expanding the Genetic Codes	Just Mix & Read Strategy: Genotyping  (SNPs)-Personalized Medicine
Fluorescent β-Lactam Antibiotics	Enediyne Anticancer Antibiotics	Chemical/Biological Sensor
Synthetic Methodology	COVID-19 INITIATIVE	Nano-Biomaterials and Nano-Photocatalysis

Graphical Abstract

Overview: In the process of the journey of synthesizing biomolecular building blocks via click chemistry, I have developed a novel “Click reagent version of Sonogashira coupling” protocol, which has a significant impact and is being utilized by several synthetic chemists globally (J. Org. Chem. 2011, 76, 2332).  The established protocol which comes with the rectification of existing limitations of Sonogashira coupling is fulfilling the demand of all chemists in the field of synthesis of conjugated alkynes. This work is highly appreciated by several renowned organic chemists in India and abroad.

• Impact of the protocol is evident from the Quote in a publication as follows: “It is noteworthy that the use of CuSO₄/sodium ascorbate was vital to prevent the generation of undesired homocoupling products of the terminal alkyne 5.” The publication is: “Total Synthesis of (−)‐Quinocarcin by Gold (I)‐Catalyzed Regioselective Hydroamination” by Prof. Hiroaki Ohno, Graduate School of Pharmaceutical Sciences, Kyoto University, Japan; published in Angew. Chem. Intl. Ed. 51, 2012, 9169-9172. Prof. Ohno had sent me a personnel greeting for the innovation and appreciated.

• Prof. I. Leray, CNRS, Université Paris Saclay, France, profoundly utilised the “click-reagent version of Sonogashira coupling” for their synthesis of Naphthalimide derivative as was reported in  Photochem. Photobiol. Sci., 16, 2017, 539. In the same paper, they also have utilised our result of calf-thymus DNA sensing by solvatochromic naphthalimides (Bag et al., Bioorg. Med. Chem. Lett., 23, 2013, 96) as a standard support of their observation.

The unique fundamental and innovative contribution in the field of Click Chemistry is also much appreciated. I have shown that the click reaction is highly efficient in the installation of a fluorescence response into a non-fluorescent precursor and modulation of the emission response of a fluorophore. Its citations appreciate the impact of the work (J. Org. Chem. 2011, 76, 3348). Prof. Wen-Sheng Chung, National Chiao Tung University, Taiwan, ROC, was greatly impressed by our work and utilsed our concept of modulation of fluorescence response of pyrene.

We have also developed strategy of one pot click and Sonogashira coupling reaction. We are also engaged in studying the reactivities of designed enediynes.

We are also engaged in studying the reactivities of triazolyl donor/acceptor fluorophore decorated monocyclic and byclic β-lactam antibiotics. We recently take up a project to decorate the nucleosides with enediynes as base and to design atropomers as new class of catalyst for assymetric synthesis.

In a continuation of the development of synthetic methodology, I have recently designed a multipurpose nano-photocatalyst [Cu^II@TiO₂] for use in carrying out Click- and hetero-selective Glaser coupling reactions in aqueous media. The beauty of the catalyst lies in its efficiency, well tolerance to a wide range of functional group and it works in environment benign solvent. Most importantly, the catalyst maintains the effective photocatalytic cycle utilizing the hole and/or oxygen in air as green oxidant for both the reactions. It is also unique for Click reaction because it works in the absence of base and has attracted immediate academic and commercial interest. This catalyst and the process is under consideration for a patent.