Synthesis of Enantiomerically Pure Nucleosides and Analogues Involving Carbohydrates as Chiral Pool

The area of carbocyclic nucleosides has developed after the isolation of (-)-aristeromycin (1) and (-)-neplanocin A (2) from natural sources showing antileukemic activity. Many of the carbocyclic nucleosides, arising from the replacement of the furanose ring oxygen by a carbon atom, exhibit interesting antiviral properties against herpes simplex virus (HSV 1 and 2), human cytomegalovirus, hepatitis B virus and human immunodeficiency virus (HIV). One of the reasons for the remarkable activities of this class of nucleosides is their better chemical as well as metabolic stability against various chemicals and enzymes. Among various analogues, carbovir (3), and abacavir (4), carboxetanocin G (5), (-)-BCA (6), BVDU (7) and carba-2/-ara-fluoroguanosine (8) show important biological properties. Carbocyclic nucleosides containing cyclohexenyl, cyclohexyl (9 and 10), and cyclopropyl (11 and 12) analogues have also been reported to be potential inhibitors of HIV, cancer and viruse

A Simple One-Pot Entry to Cyclic Ethers of Varied Ring Sizes From Diols via Phosphonium Ion Induced Iodination and Base Catalyzed Williamson Etherification

A novel and an efficient one-pot cyclization method using triphenylphosphine, iodine and a nitrogenous base has been established for the synthesis of cyclic ethers of various ring sizes. This appears to follow a two-step procedure, which includes preferential substitution of one hydroxyl group by an iodide generated in situ followed by an intramolecular ring closure through the attack of a free hydroxyl group or the more nucleophilic oxide ion

A simple cleft shaped hydrazine-functionalized colorimetric new Schiff base chemoreceptor for selective detection of F− in organic solvent through PET signaling: Development of a chemoreceptor based sensor kit for detection of fluoride

Novel colorimetric hydrazine-functionalized Schiff base chemoreceptor [N1N3bis(perfluorobenzylidene)isophthalahydrazide] NBPBIH has been prepared for selective detection of F−. In this receptor more NH and CN units are incorporated for better colorimetric responses as compared to systems having lesser number of such units. NBPBIH turns from colorless to dark yellow on exposure to F−. The detection event is well supported by UV–vis, fluorescence, 1H and 19F-NMR like spectrophotometric and cyclic voltammetric studies in DMSO because of enhanced fluorescence responses, higher Stokes shift value and for its less toxic nature compared to other solvents. Quenching of fluorescence is explained with photoinduced electron transfer mechanism (PET). The binding constant of NBPBIH with F− is around 0.84 × 105 M−1 and limit of detection of F− is found 1.42 × 10−5 M. Our concern is also to address fluorosis: an issue related to global health problem, affecting millions of common people. It is noteworthy that the existing diagnostic and treatment options are of huge expenses. As an artefact, chemoreceptor assisted simple prototype for detecting excessive fluoride in sample solution has been designed and developed which has potential and good prospect to be applied as a low cost affordable diagnostic kit for fluorosis in largely affected countries like China, India and several others

Colorimetric and fluorimetric response of Schiff base molecules towards fluoride anions, solution test kit fabrication, logical interpretation and DFT-D3 study

Two newly synthesized Schiff base molecules are herein reported as anion sensors. –NO2 substituted receptor (P1) is comparatively more acidic and can sense F−, OAc− and H2PO4−, whereas –CN substituted receptor (P2) is less acidic and is selective for F− only. Reversible UV-Vis response for both receptors with F− can mimic multiple logic gate functions, and several complex electronic circuits based on XNOR, XOR, OR, AND, NOT and NOR logic operations with ‘Write–Read–Erase–Read’ options have been executed. Interesting ‘turn on and off’ fluorescence responses were noticed for the receptors with F−. Intracellular F− detection as a diagnosis of non-skeletal fluorosis was successful using a fluorescence microscope with Candida albicans (prokaryotic cell, a diploid fungus) and pollen grains of Tecoma stans (eukaryotic cell) incubated in 10−6 M fluoride-contaminated hand-pump water collected from Bankura, West Bengal, India. Furthermore, a solution test kit was fabricated for easy and selective detection of F− in an aqueous solvent

A simple and dual responsive efficient new Schiff base chemoreceptor for selective sensing of F− and Hg2+: application to bioimaging in living cells and mimicking of molecular logic gates

A novel colorimetric hydrazine-functionalized Schiff base chemoreceptor, NPMP, was synthesized following a simple one-step Schiff base condensation pathway. NPMP showed selective colorimetric change from faint yellow to yellowish orange in the presence of biologically ubiquitous fluoride (F−). It also showed a ‘turn off’ fluorescent response in the presence of F− that could effectively distinguish it from all anions tested except acetate. Acetate (OAc−) caused a weak response, while other anions like chloride, bromide, iodide, phosphate, hydrogen sulfate and nitrate did not have any observable effect on the NPMP receptor (E)-4-nitro-2-((2-(perfluorophenyl)hydrazono)methyl)phenol. Recognition of F− in the presence of NPMP can be explained in light of multiple H-bonding interactions, as well as acid–base interactions between host receptor and guest F−. Interestingly, NPMP also showed enormous potential as a staining agent in determining the presence of low levels of intracellular fluoride. Moreover, it was found that in NPMP⋯F− solutions, incorporation of Hg2+ showed observable optical changes, revealing that this compound is a smart material. Optical responses of NPMP can mimic a molecular logic gate (INHIBIT gate). This can be interpreted as a combination of an AND gate with a NOT function. It also represented a potential ‘Write–Read–Erase–Read’ memory function reflecting multi-writing ability

Cell permeable fluorescent colorimetric Schiff base chemoreceptor for detecting F−in aqueous solvent

A novel colorimetric hydrazine based Schiff base chemoreceptor (E)-2-((2-(perfluorophenyl)hydrazono)methyl)phenol (PMP), for detection of fluoride (F−) is reported in this work. The receptor can selectively detect F− by turning from colorless to yellow. The recognition event is further confirmed by solution state spectrophotometric measurements like UV–Vis, Fluorescence and 1H NMR titrimetric studies. The fluorescence ‘turn on’ phenomenon of PMP with gradual addition of F− can be well explained by inhibition of Cdouble bond; length as m-dashN isomerization process. 1H NMR titration experiments of PMP with F− further support the hydrogen bonding interaction between host PMP and guest F−. Interestingly, PMP has potential toward detection of intracellular F− in cells of Candida albicans (diploid fungus) and pollen grains of Techoma stans. The recognition phenomenon is reversible and we have successfully developed two input logic network where INHIBIT gate can be considered as an AND gate with one input inverted by a NOT function. Furthermore, this logic gate represents a potential ‘Write-Read-Erase-Read’ memory function possessing multi writing ability

Hydrazine functionalized probes for chromogenic and fluorescent ratiometric sensing of pH and F−: experimental and DFT studies

Two novel hydrazine based sensors, BPPIH (N1,N3-bis(perfluorophenyl)isophthalohydrazide) and BPBIH (N1′,N3′-bis(perfluorobenzylidene)isophthalohydrazide), are presented here. BPPIH is found to be a highly sensitive pH sensor in the pH range 5.0 to 10.0 in a DMSO–water solvent mixture with a pKa value of 9.22. Interesting optical responses have been observed for BPPIH in the above mentioned pH range. BPBIH on the other hand turns out to be a less effective pH sensor in the above mentioned pH range. The increase in fluorescence intensity at a lower pH for BPPIH was explained by using density functional theory. The ability of BPPIH to monitor the pH changes inside cancer cells is a useful application of the sensor as a functional material. In addition fluoride (F−) selectivity studies of these two chemosensors have been performed and show that between them, BPBIH shows greater selectivity towards F−. The interaction energy calculated from the DFT-D3 supports the experimental findings. The pH sensor (BPPIH) can be further interfaced with suitable circuitry interfaced with desired programming for ease of access and enhancement of practical applications

Synthesis and in vitro antiviral evaluation of 4-substituted 3,4-dihydropyrimidinones

A series of 4-substituted 3,4-dihydropyrimidine-2-ones (DHPM) was synthesized, characterized by IR, (1)H NMR, (13)C NMR and HRMS spectra. The compounds were evaluated in vitro for their antiviral activity against a broad range of DNA and RNA viruses, along with assessment for potential cytotoxicity in diverse mammalian cell lines. Compound 4m, which possesses a long lipophilic side chain, was found to be a potent and selective inhibitor of Punta Toro virus, a member of the Bunyaviridae. For Rift Valley fever virus, which is another Bunyavirus, the activity of 4m was negligible. DHPMs with a C-4 aryl moiety bearing halogen substitution (4b, 4c and 4d) were found to be cytotoxic in MT4 cells.publisher: Elsevier articletitle: Synthesis and in vitro antiviral evaluation of 4-substituted 3,4-dihydropyrimidinones journaltitle: Bioorganic & Medicinal Chemistry Letters articlelink: http://dx.doi.org/10.1016/j.bmcl.2016.12.010 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved.status: publishe