Wittig and Wittig-Horner reactions under phase transfer catalysis conditions

Wittig and Wittig-Horner reactions are favorite tools in preparative organic chemistry. These olefination methods enjoy widespread and recognition because of their simplicity, convenience, and effciency. Phase transfer catalysis (PTC) is a very important method in synthetic organic chemistry having many advantages over conventional, homogenous reaction procedures. In this paper, we attempt to summarize the aspects concerning Wittig and Wittig-Horner reactions that take place under phase transfer catalysis conditions.     

Isolation and characterization of a novel lepidopteran-selective toxin from the venom of South Indian red scorpion, Mesobuthus tamulus

Background

Scorpion venom contains insect and mammal selective toxins. We investigated the venom of the South Indian red scorpion, Mesobuthus tamulus for the purpose of identifying potent insecticidal peptide toxins.

Results

A lepidopteran-selective toxin (Buthus tamulus insect toxin; ButaIT) has been isolated from this venom. The primary structure analysis reveals that it is a single polypeptide composed of 37 amino acids cross-linked by four disulfide bridges with high sequence homology to other short toxins such as Peptide I, neurotoxin P2, Lqh-8/6, chlorotoxin, insectotoxin I5A, insect toxin 15 and insectotoxin I1. Three dimensional modeling using Swiss automated protein modeling server reveals that this toxin contains a short α-helix and three antiparallel β-strands, similar to other short scorpion toxins. This toxin is selectively active on Heliothis virescens causing flaccid paralysis but was non-toxic to blowfly larvae and mice.

Conclusion

This is the first report of a Heliothine selective peptide toxin. Identification of diverse insect selective toxins offer advantages in employing these peptides selectively for pest control.     

Long-term effects of human induced pluripotent stem cell-derived retinal cell transplantation in Pde6b knockout rats

Retinal degenerative disorders, including age-related macular degeneration and retinitis pigmentosa (RP), are characterized by the irreversible loss of photoreceptor cells and retinal pigment epithelial (RPE) cells; however, the long-term effect of implanting both human induced pluripotent stem cell (hiPSC)-derived RPE and photoreceptor for retinal regeneration has not yet been investigated. In this study, we evaluated the long-term effects of hiPSC-derived RPE and photoreceptor cell transplantation in Pde6b knockout rats to study RP; cells were injected into the subretinal space of the right eyes of rats before the appearance of signs of retinal degeneration at 2–3 weeks of age. Ten months after transplantation, we evaluated the cells using fundus photography, optical coherence tomography, and histological evaluation, and no abnormal cell proliferation was observed. A relatively large number of transplanted cells persisted during the first 4 months; subsequently, the number of these cells decreased gradually. Notably, immunohistochemical analysis revealed that the hiPSC-derived retinal cells showed characteristics of both RPE cells and photoreceptors of human origin after transplantation. Functional analysis of vision by scotopic electroretinogram revealed significant preservation of vision after transplantation. Our study suggests that the transplantation of hiPSC-derived retinal cells, including RPE cells and photoreceptors, has a potential therapeutic effect against irreversible retinal degenerative diseases.Subject terms: Translational research, Stem-cell research, Retina     

Effect of nano-size fumed silica on ionic conductivity of PVdF-HFP-based plasticized nano-composite polymer electrolytes

Nano-composite polymer electrolytes containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), ammonium tetrafluoroborate (NH₄BF₄), and nano-size fumed silica (SiO₂) have been prepared and characterized by complex impedance spectroscopy. Ionic conductivity of polymer has been found to increase with the addition of NH₄BF₄, and a maximum conductivity of 3.62 × 10^?6 S/cm has been obtained at 30 wt% NH₄BF₄. The formation of ion aggregates at high concentration of salt has been explained by Bjerrum’s law and mass action considerations. The conductivity of polymer electrolytes has been increased by three orders of magnitude (10^?6 to 10^?3 S/cm) with the addition of plasticizer, and a maximum conductivity of 1.10 × 10^?3 S/cm has been observed at 80 wt% DMA. An increase in conductivity with the addition of nano-size fumed silica is attributed due to the formation of space-charge layers. A maximum conductivity of 7.20 × 10^?3 S/cm has been observed for plasticized nano-composite polymer electrolytes at 3 wt% SiO₂. X-ray diffraction analysis of polymer electrolyte system was also carried out. A small change in conductivity of nano-composite polymer electrolytes observed over the 30–130 °C temperature range and for a period of 30 days is also desirable for their use in various applications.     

Total synthesis and selective activity of a new class of conformationally restrained epothilones

Stereoselective total syntheses of two novel conformationally restrained epothilone analogues are described. Evans asymmetric alkylation, Brown allylation, and a diastereoselective aldol reaction served as the key steps in the stereoselective synthesis of one of the two key fragments of the convergent synthetic approach. Enzyme resolution was employed to obtain the second fragment as a single enantiomer. The molecules were assembled by esterification, followed by ring-closing metathesis. In preliminary cytotoxicity studies, one of the analogues showed strong and selective growth inhibitory activity against two leukemia cell lines over solid human tumor cell lines. The precise biological mechanism of action and high degree of selectivity of this analogue remain to be examined.     

Chlorotrimethylsilane catalyzed synthesis of 1,3-diphenyl-2-propenones and their antimicrobial activities

The base- or acid-catalyzed Claisen–Schmidt condensation reaction is the common synthetic route for the synthesis of 1,3-diphenyl-2-propenone (known as chalcone). A variety of different synthetic pathways have been used over the decades in the synthesis of chalcone. Microwave irradiation in absence of solvent is employed successfully and presented here with prominent improvement over the existing methods. The reaction is incredibly accelerated in the presence of the catalyst chlorotrimethylsilane (CTMS) and found superior in terms of reaction time, product yield, safer synthetic route, and easy removal of catalyst etc. Products were characterized by elemental analysis and spectroscopy. Single crystal X-ray diffraction was used to determine crystal structures. All compounds were treated for antimicrobial activity. The profound response against bacteria and fungus pathogens by these compounds is impressive and opens up opportunities for further physiological activity studies.     

Effect of heat treatment on thermal and mechanical stability of NaOH-doped xanthan gum-based hydrogels

Journal of Solid State Electrochemistry - Xanthan gum (XG)-based hydrogels containing sodium hydroxide (NaOH) salt were synthesized with the use of distilled water (DW) at room temperature and...     

Bianchi type IX string cosmological model in general relativity

We have investigated Bianchi type IX string cosmological models in general relativity. To get a determinate solution, we have assumed a condition ρ=λ i.e. rest energy density for a cloud of strings is equal to the string tension density. The various physical and geometrical aspects of the models are also discussed.     

Quantitative and Qualitative Analysis of CKD-501, Lobeglitazone, in Human Plasma and Urine Using LC–MS/MS and Its Application to a Pharmacokinetic Study

A simple, rapid and sensitive LC–MS/MS method in positive ion mode was developed and validated to determine CKD-501, lobeglitazone, in human plasma and urine using glipizide as an internal standard (IS). Lobeglitazone is a novel thiazolidinedione (TZDs)-based peroxisome proliferator-activated receptor (PPAR) agonist, used for the management of type-2 diabetes. After mixing the IS, dissolved in acetonitrile, with a plasma or urine sample containing lobeglitazone, 10?μL of supernatant was injected into the LC–MS/MS system. Quantification was performed in the multiple reaction monitoring (MRM) mode using transition of 481.5?→?152.2 (m/z) for lobeglitazone and 446.1?→?321.2 (m/z) for the IS. The method showed good linearity over concentration ranges of 0.5–1,000?ng?mL^?1 for plasma and 0.2–250?ng?mL^?1 for urine (r ²?≥?0.9996). The mean percent extraction recovery of lobeglitazone was 90.8?% for plasma and 87.3?% for urine, while the recoveries of the IS were greater than 86.4?% for both. The intra-day and inter-day precision of plasma ranged from 1.1 to 3.7 and 2.5 to 3.3?% (RSD), respectively, and the intra- and inter-day precision of urine ranged from 1.5 to 2.7 and 3.2 to 3.5?%, respectively. This method is simple, sensitive, and applicable for the pharmacokinetic study of lobeglitazone in human plasma. Most of the urine concentrations of lobeglitazone were below the LLOQ because the lobeglitazone is extensively metabolized.