Recent Methods for Synthesis of Coumarin Derivatives and Their New Applications

Coumarin (2H-1-benzopyran-2-one) and its heterocyclic derivatives are widely used as lactone scaffolds used by innovative methods for the preparation of heterocyclic molecules. Nowadays, significant biological activities, as well as properties of unique nature coumarin derivatives, have played an important role in the development of novel drugs. This chapter entitles numerous methods of one-pot construction of coumarin derivatives, together with well-known name reactions and other type reactions as well, in the presence of various metal-based homogenous and heterogeneous catalyst system. Coumarin is one of the very important heterocycles and its analogs like natural product and pharmaceutically active drug molecules are extracted/isolated from a plants, animals, and microbes. Coumarin precursors have a wide range of biological activities Hence, the synthesis of coumarins and their heterocyclic analogs have become among the most interesting compound over the last many years in the growth of improved synthetic methodologies to form different types of functional groups that are present in coumarins derivatives. The synthesis of coumarins enabled by current approaches and their most recent bio-applications are discussed in this book chapter. Corresponding complex heterocycles-based coumarin analogs are produced from substituted alkyne substrates and other starting materials as well

Quadrol-Pd(II) complexes: phosphine-free precatalysts for the room-temperature Suzuki-Miyaura synthesis of nucleoside analogues in aqueous media

Commercially available Quadrol, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (THPEN), has been used for the first time as N^N- donor neutral hydrophilic ligand in the synthesis and characterization of new water soluble palladium (II) complexes containing chloride, phthalimidate or saccharinate as co-ligands. [PdCl2(THPEN)] (1) [Pd(phthal)2(THPEN)] (2), [Pd(sacc)2(THPEN)] (3) and the analogous complex with the closely related N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine (THEEN) [Pd(sacc)2(THEEN)] (4) were efficiently prepared in a one-pot reaction from [PdCl2(CH3CN)2] or Pd(OAc)2. Structural characterization of 1 and 3 by single crystal X-ray diffraction produced the first structures reported to date of palladium complexes with Quadrol. The resultant palladium complexes are highly soluble in water and were found to be effective as phosphine-free catalysts for the synthesis of functionalized nucleoside analogues under room-temperature Suzuki-Miyaura cross-coupling conditions between 5-iodo-2'-deoxyuridine (& 5-iodo-2'-deoxycytidine) with different aryl boronic acids in neat water. This is the first report of the coupling process performed on nucleosides in water at room temperature.This work has been partially supported by RTI2018-098233-B-C21 (MICINN) and 20790/PI/18 (Fundación SENECA CARM) grants. A.R.K would like to acknowledge SERB for EMR grant (EMR/2016/005439). Professor Gregorio Sánchez, who recently passed away, is gratefully acknowledged for his contribution to this work and his wise and continuous advice and support

Recent advancements in metal-organic frameworks integrating quantum dots (QDs@MOF) and their potential applications

Design and development of new materials and their hybrids are key to addressing current energy issues. Thanks to their tunable textural and physiochemical properties, metal-organic frameworks (MOFs) show great potential toward gas sorption, catalysis, sensing, and electrochemical energy applications. Nevertheless, practical applications of MOFs have been hampered because of their limited electrical conductivity, micropore size, and poor stability. However, smart integration of zero-dimensional quantum dots (QDs) into an MOF template, where the host structure offers suitable interactions for enhancing the stability and synergic properties, may be a solution. The objective of this review is to summarize recent advances in the field of QD@MOFs, highlighting fresh approaches to synthesis strategies and progress made in their application to optoelectronic devices, sensing, biomedical, catalysis, and energy storage. The current challenges and future directions of QDs@MOFs hybrids toward advancing energy and environmental applications are also addressed. We anticipate that this review will inspire researchers to develop novel MOF hybrids for energy, optoelectronics, and biomedical applications.Web of Science1111976194

Imaging <i>Pseudomonas aeruginosa</i> Biofilm Extracellular Polymer Scaffolds with Amphiphilic Carbon Dots

Biofilm formation is a critical facet of pathogenesis and resilience of human, animal, and plant bacteria. Extracellular polymeric substances (EPS) constitute the physical scaffolding for bacterial biofilms and thus play central roles in their development and virulence. We show that newly synthesized amphiphilic fluorescent carbon dots (C-dots) readily bind to the EPS scaffold of <i>Pseudomonas aeruginosa</i>, a major biofilm-forming pathogen, resulting in unprecedented microscopic visualization of the EPS structural features. Fluorescence microscopy analysis utilizing the C-dots reveals that the <i>P. aeruginosa</i> EPS matrix exhibits a remarkable dendritic morphology. The experiments further illuminate the growth kinetics of the EPS and the effect of external factors such as temperature. We also show that the amphiphilic C-dot platform enabled screening of substances disrupting biofilm development, specifically quorum sensing inhibitors

Designing of Gradient Scaffolds and their Applications in Tissue Regeneration

Gradient scaffolds are isotropic/anisotropic three-dimensional structures with gradual transitions in geometry, density, porosity, stiffness, etc., that mimic the biological extracellular matrix. The gradient structures in bio-logical tissues play a major role in various functional and metabolic activities in the body. The designing of gradients in the scaffold can overcome the current challenges in the clinic compared to conventional scaffolds by exhibiting excellent penetration capacity for nutrients & cells, increased cellular adhesion, cell viability & dif-ferentiation, improved mechanical stability, and biocompatibility. In this review, the recent advancements in designing gradient scaffolds with desired biomimetic properties, and their implication in tissue regeneration applications have been briefly explained. Furthermore, the gradients in native tissues such as bone, cartilage, neuron, cardiovascular, skin and their specific utility in tissue regeneration have been discussed in detail. The insights from such advances using gradient-based scaffolds can widen the horizon for using gradient biomaterials in tissue regeneration applications

Immunoediting role for major vault protein in apoptotic signaling induced by bacterial N-acyl homoserine lactones.

The major vault protein (MVP) mediates diverse cellular responses, including cancer cell resistance to chemotherapy and protection against inflammatory responses to Pseudomonas aeruginosa Here, we report the use of photoactive probes to identify MVP as a target of the N-(3-oxo-dodecanoyl) homoserine lactone (C12), a quorum sensing signal of certain proteobacteria including P. aeruginosa. A treatment of normal and cancer cells with C12 or other N-acyl homoserine lactones (AHLs) results in rapid translocation of MVP into lipid raft (LR) membrane fractions. Like AHLs, inflammatory stimuli also induce LR-localization of MVP, but the C12 stimulation reprograms (functionalizes) bioactivity of the plasma membrane by recruiting death receptors, their apoptotic adaptors, and caspase-8 into LR. These functionalized membranes control AHL-induced signaling processes, in that MVP adjusts the protein kinase p38 pathway to attenuate programmed cell death. Since MVP is the structural core of large particles termed vaults, our findings suggest a mechanism in which MVP vaults act as sentinels that fine-tune inflammation-activated processes such as apoptotic signaling mediated by immunosurveillance cytokines including tumor necrosis factor-related apoptosis inducing ligand (TRAIL)