Shashank Shekhar
@University of Delhi
Researcher, Department of Chemistry
NETAJI SUBHAS INSTITUTE OF TECHNOLOGY
EDUCATION
Doctoral in Chemistry from University of Delhi, India
RESEARCH INTERESTS
Analytical Chemistry and Materials Chemistry, Polymers
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Shashank Shekhar, Sanjeev Gautam, Bhasha Sharma, Shreya Sharma, Partha Pratim Das, and Vijay Chaudhary
Elsevier BV
Shashank Shekhar, Shreya Sharma, Amit Kumar, Anjali Taneja, and Bhasha Sharma
Royal Society of Chemistry (RSC)
Nanotechnology has imparted excellent substitutes in the area of agriculture for the management of insect pests without deteriorating the surrounding biota and thereby allows a more verdant environment.
Bhasha Sharma, Shashank Shekhar, Shreya Sharma, and Purnima Jain
Elsevier BV
Bhasha Sharma, Yagyadatta Goswami, Shreya Sharma, and Shashank Shekhar
Elsevier BV
Shashank Shekhar, Tonia S. Ahmed, Andrew R. Ickes, and Michael C. Haibach
American Chemical Society (ACS)
Shreya Sharma, Shashank Shekhar, Sanjeev Gautam, K. D. Chauhan, and Bhasha Sharma
Springer Science and Business Media LLC
The emanating paragon of personalized medical care utilizes discrete patient data to customize clinical therapy. While the principal cynosure so far is the formulation of ameliorated therapeutics contingent on “omics” data, the notion outstretches all embodiments of customized treatment. Howbeit, the dearth of in vitro tissue and organ models competent of mimicking human physiology gravely impede the development and clinical translation of drugs and therapies with higher in vivo efficiency. Bioprinting (a form of additive manufacturing) enables us to effectively address the perpetual limitations for the manufacturing of hierarchically organized living constructs with complex structural and functional organization through the precise spatial positioning of multiple materials and cells. Additive manufacturing translates computer-aided design virtual 3D models into physical objects. By digital splicing of tomographic data, 3D scan, or computer-aided design, layer-by-layer fabrication of target objects can be achieved bereft the requirement for molds or machining. As polymeric materials are by far the most exploited class of materials, the anecdote discusses the processing of polymers and the development of polymers and advanced polymeric systems, especially for bioprinting. Facets of polymer design, additives, and processing parameters as they harmonize to exalting build speed and improved veracity, stability, functionality, mechanical attributes, porosity, and surface finish are explored. As the field matures, additive manufacturing is poised to proffer patient-specific tissue and organ substitutes, reproducible microtissues for drug screening and disease modeling, personalized drug delivery systems, as well as customized medical devices; therefore, we also highlight the most pressing challenges facing the research domain to revolutionize modern medicine and healthcare.
Shashank Shekhar, Amarendra Mohan Khan, Shreya Sharma, Bhasha Sharma, and Anjana Sarkar
Springer Science and Business Media LLC
The proliferation in cancer and multidrug-resistant infections amidst personage with the evolution of civilization is an alarming bone of contention. Cancer has long been the pre-eminent core of death worldwide; additionally, it paves the way for a large portion of the microbial infections, hence increasing the implications. Nonetheless, the wide rate of multidrug opposition in both diseases entails the progression of potential molecules with intended characteristics that could dodge multidrug-resistant issues. A fruitful methodology for chemotherapy has been the employment of drugs with metal as active ingredients that can be utilized to treat multi-resistant infections more effectively. Schiff bases have been imperative, inferable from their adaptable metal chelating properties, innate organic exercises, and adaptability to alter the structure to tweak it for specific natural applications. With the advent of the modern pharmaceutical industry, biochemical approaches to forestalling and treating disease have procured a new level of prominence in the evolving relationship between microbes and their human hosts. This review gives an insight into some indispensable biological aspects of Schiff bases in light of their antibacterial and anticancer activity and discusses the potential and eventual fate of this class of metallodrugs either as anticancer or antimicrobial specialists.
Alison M. Wilders, Jeremy Henle, Michael C. Haibach, Rafal Swiatowiec, Jeffrey Bien, Rodger F. Henry, Shardrack O. Asare, Amanda L. Wall, and Shashank Shekhar
American Chemical Society (ACS)
Biaryl phosphorinane ligands derived from addition of biaryl primary phosphines to trans,trans-dibenzylideneacetone (AlisonPhos and AliPhos) form highly active ligands for Pd-catalyzed coupling of ...
Michael C. Haibach, Andrew R. Ickes, Alison M. Wilders, and Shashank Shekhar
American Chemical Society (ACS)
This highlight is the second installment of a series of highlights on nonprecious-metal-catalyzed reactions of interest to the pharmaceutical industry. Selected transformations from March to June 2...
Le Wang, George A. Doherty, Andrew S. Judd, Zhi-Fu Tao, T. Matthew Hansen, Robin R. Frey, Xiaohong Song, Milan Bruncko, Aaron R. Kunzer, Xilu Wang,et al.
American Chemical Society (ACS)
Herein we describe the discovery of A-1331852, a first-in-class orally active BCL-XL inhibitor that selectively and potently induces apoptosis in BCL-XL-dependent tumor cells. This molecule was generated by re-engineering our previously reported BCL-XL inhibitor A-1155463 using structure-based drug design. Key design elements included rigidification of the A-1155463 pharmacophore and introduction of sp3-rich moieties capable of generating highly productive interactions within the key P4 pocket of BCL-XL. A-1331852 has since been used as a critical tool molecule for further exploring BCL-2 family protein biology, while also representing an attractive entry into a drug discovery program.
Atanu Modak, Alex J. Nett, Elizabeth C. Swift, Michael C. Haibach, Vincent S. Chan, Thaddeus S. Franczyk, Shashank Shekhar, and Silas P. Cook
American Chemical Society (ACS)
Copper, an earth-abundant metal, has reemerged as a viable alternative to the versatile Pd-catalyzed C–N coupling. Coupling sterically hindered reaction partners, however, remains challenging. Here...
Shreya Sharma, Shashank Shekhar, Bhasha Sharma, and Purnima Jain
Royal Society of Chemistry (RSC)
A glycan toolbox for pathogenic and cancerous interventions. The review article sheds light on the sweet secrets of this complex structure.
Jeffrey M. Kallemeyn, Kenneth M. Engstrom, Matthew J. Pelc, Kirill A. Lukin, Westin H. Morrill, Haojuan Wei, Timothy B. Towne, Jeremy Henle, Nandkishor K. Nere, Dennie S. Welch,et al.
American Chemical Society (ACS)
Glecaprevir was identified as a potent HCV protease inhibitor and a large-scale synthesis was required to support the late stage clinical trials and subsequent commercial launch. The large-scale sy...
Elizabeth C. Swift, Shashank Shekhar, and Brian J. Kotecki
American Chemical Society (ACS)
A general method to prepare valuable chiral synthon β-aryl-β-aryloxy esters from enantioselective hydrogenation of (E)-β-aryl-β-aryloxy-α,β-unsaturated esters is described. The E-isomer was prepared via isomerization of the mixture of E- and Z-isomers using photocatalyst [Ir(ppy)2(dtbbpy)]PF6. A laser as the light source facilitated isomerization with only 0.05 mol % catalyst. The enantioselective hydrogenation was conducted with (NBD)2Rh(BF4) and a commercially available Josiphos ligand to provide the synthons in up to 95% yield with 97% ee.
Shashank Shekhar, Reetu Sharma, Shreya Sharma, Bhasha Sharma, Anjana Sarkar, and Purnima Jain
Elsevier BV
Shashank Shekhar, Anjana Sarkar, Bhasha Sharma, and Purnima Jain
Wiley
Sebastien Monfette, Adam R. Brown, Pascal Dubé, Nathan D. Ide, Chad A. Lewis, Jared L. Piper, Shashank Shekhar, and Shu Yu
Wiley
Joshua D. Laffoon, Vincent S. Chan, Michael G. Fickes, Brian Kotecki, Andrew R. Ickes, Jeremy Henle, José G. Napolitano, Thaddeus S. Franczyk, Travis B. Dunn, David M. Barnes,et al.
American Chemical Society (ACS)
We report the use of biaryl phosphorinanes as ligands for Pd-catalyzed cross-coupling reactions. A modular synthesis was developed that employs a double conjugate addition of primary biaryl phosphines into 1,1,5,5-tetraalkyl penta-1,4-diene-3-ones. Notably, this synthesis does not require the use of copper, a known contaminant in structurally related biaryl phosphane ligands. Using the synthetic strategy described above, we synthesized a library of biaryl phosphorinanes, varying their substitution about phosphorus and the steric and electronic nature of the biaryl motif. We then benchmarked their performance as ligands in Pd-catalyzed cross coupling reactions such as aryl sulfonamidation, aryl alkoxylation, and aryl amination in the presence of soluble organic bases. In each reaction studied, many ligands outperformed biaryl phosphanes known to promote the given transformation. Detailed substrate scopes were determined using high-throughput screening technology. Several biaryl phosphorinanes and their cor...
Daniel D. Caspi, Moiz Diwan, Jean-Christophe C. Califano, Daniel J. Mack, and Shashank Shekhar
American Chemical Society (ACS)
Rigorous understanding of the impact of reaction parameters on the formation and rejection of impurities in a reaction is a critical part of process development. The fate of impurities is often governed by multivariate interactions of reaction parameters, making the design and development of an operational space an arduous task. We describe development of an operational space for a Pd-catalyzed amidation reaction used in the synthesis of ABT-530. A mathematical model was developed to delineate the impact of a large number of reaction parameters (8) on the formation of the amidation product 3 as well as the most persistent impurity, Phenol (7). The model identified a very high risk of formation of 7 in greater than acceptable level because of slight variations from the nominal reaction conditions. Guided by the model, new nominal conditions for the amidation reaction were identified and a broad and robust operational space was established from the combination of experimental and modeling work.
David M. Barnes, Shashank Shekhar, Travis B. Dunn, Jufang H. Barkalow, Vincent S. Chan, Thaddeus S. Franczyk, Anthony R. Haight, John E. Hengeveld, Lawrence Kolaczkowski, Brian J. Kotecki,et al.
American Chemical Society (ACS)
Dasabuvir (1) is an HCV polymerase inhibitor which has been developed as a part of a three-component direct-acting antiviral combination therapy. During the course of the development of the synthetic route, two novel coupling reactions were developed. First, the copper-catalyzed coupling of uracil with aryl iodides, employing picolinamide 16 as the ligand, was discovered. Later, the palladium-catalyzed sulfonamidation of aryl nonaflate 33 was developed, promoted by electron-rich palladium complexes, including the novel phosphine ligand, VincePhos (50). This made possible a convergent, highly efficient synthesis of dasabuvir that significantly reduced the mutagenic impurity burden of the process.
Bhasha Sharma, Sanjeev Gautam, Shashank Shekhar, Rukmani Sharma, Deepak Singh Rajawat, and Purnima Jain
Elsevier BV
John F. Hartwig, Kevin H. Shaughnessy, Shashank Shekhar, and Rebecca A. Green
Wiley
Bhasha Sharma, Shashank Shekhar, Sanjeev Gautam, Anjana Sarkar, and Purnima Jain
Elsevier BV
Bhasha Sharma, Shashank Shekhar, Sanjeev Gautam, and Purnima Jain
Elsevier BV
Bhasha Sharma, Shashank Shekhar, Parul Malik, and Purnima Jain
IOP Publishing
Graphene, a wonder material has inspired quest among researchers due to its numerous applications and exceptional properties. This paper highlights the mechanism and chemistry behind the fabrication of graphene oxide by using phosphoric acid. Chemical functionalization is of prime importance which avoids agglomeration of nanoparticles to attain inherent properties. As non-homogeneous dispersion limits its utilization due to interfacial interactions which restrict reactive sites to produce intercalated network. Thus, chemically functionalized graphene leads to stable dispersion and enhances thermal, mechanical and electrical properties of the resultant polymer composite materials. Solubility of graphene in aqueous solution is the major issue because graphene is hydrophobic, to rectify this oxygen containing hydrophilic groups must be introduced to make it compatible and this can be attained by covalent functionalization. Among all nanofiller GO has shown average particle size i.e. 95 nm and highest surface charge density. The characteristic changes were estimated using Raman spectra.