Stereoselective total synthesis of Jaspine B (Pachastrissamine) utilizing iodocyclization and an investigation of its cytotoxic activity

The stereoselective synthesis of Jaspine B has been achieved from easily available (S)-Garner’s aldehyde. The trisubstituted tetrahydrofuran core of Jaspine B was constructed by utilizing a diastereoselective iodocyclization as the key step. Deiodination and debenzylation were performed in a single step by using n-Bu₃SnH and ABCN as a conjugate catalyst system. The in vitro cytotoxicity of compounds 1 and 1a against 3 human cancer cell lines-A549 (lung), MCF7 (breast), and KB (oral); and a non-cancer cell line (NIH3T3) was determined by sulphorhodamine B based assay.     

Single channel tunable wavelength demultiplexer using nonlinear one dimensional defect mode photonic crystal

Transmission characteristics of nonlinear one dimensional photonic crystal with a defect have been studied. GaAs/Si multilayer structure with a single defect has been simulated using transfer matrix method. In this study refractive indices of both layers have been taken to be dependent on intensity and wavelength simultaneously. It is found that central wavelength of defect mode change with intensity of wave. Average change in central wavelength of defect mode is 0.02 nm/(1 GW/cm²). This property can be exploited in the design of a single channel tunable wavelength division demultiplexer for optical communication.     

A strategy to access fused triazoloquinoline and related nucleoside analogues

Fused triazoloquinolines have been prepared starting from (E)-3-(2-nitrophenyl)-1-aryl-prop-2-en-1-ones and sugar or benzyl azides in a sequential [3+2] cycloaddition reaction, followed by one pot Pd–C assisted reduction, cyclization and aromatization. The triazolyl fused quinolines with N¹-glycosyl substituents as unnatural nucleosides have inherent potential to generate a library of compounds for bioevaluations.     

Nonlinear Taft Polar Free Energy Relationship: Reactions of N‐Substituted Benzyl Amines with Benzyl Bromide in Methanol

The rates of reactions of N‐substituted benzyl amines with benzyl bromide were measured using a conductivity technique in methanol medium. The reaction followed a total second‐order path. The end product of the reaction is identified as dibenzyl alkyl amine (C₆H₅CH₂N(R)CH₂C₆H₅). The rates increased with a decrease in the electron‐donating capacity or with an increase in the Taft σ* value of electron‐donating alkyl substituents (R) such as t‐butyl (σ* = ?0.3), i‐propyl (σ* = ?0.19), n‐butyl (σ* = ?0.13), and ethyl (σ* = ?0.1) on nitrogen of the amine until the Taft σ* value becomes zero for the methyl group ( = 0.00), and then the rates decreased with an increase in the electron‐withdrawing capacity or with an increase in the Taft σ* value of electron‐withdrawing substituents (R) such H and C₆H₅ ( = 0.49 and = 0.6). The locus of the Taft polar free energy relationship has a maximum near the point for N‐methyl benzyl amine, showing that there is a sharp change in the rate‐determining step. A mechanism involving formation of an S_N2‐type transition state between the amine nucleophiles and the benzyl bromide and its subsequent decomposition is proposed. Activation parameters were calculated and are discussed.     

Synthesis and Enzyme Inhibitory Activities of Highly Functionalized Pyridylmethyl-C-β-D-Glycosides

Several pyridylmethyl-C-β-D-glycosides (3a–3l, 6a, and 6h) were synthesized by refluxing 3-(β-D-glucopyranosyl)/(β-D-cellobiosyl)-propanones and dicyanobenzylidenes with ammonium acetate in anhydrous toluene in moderate to good yields. The reaction involves a C?C Michael addition of enamine, formed from glycosyl ketone and ammonium acetate, to the dicayanobenzylidene derivative; subsequent dehydrative cyclization; and oxidative aromatization. Two of these prototypes, compounds 3e and 3k, were deacetylated to the respective glucopyranosyl methyl pyridines 4e and 4k with NaOMe/MeOH. The synthesized compounds were screened for their in vitro α-glucosidase inhibitory activities and one of the compounds showed 20% inhibition as compared to standard drug acarbose displaying 39% inhibition.     

Syntheses of Branched Non‐1‐ynitols by Chemoselective Addition of (Trimethylsilyl)‐propargylmagnesium Bromide at the Anomeric Center of Side Chain Halogeno Functionalized Carbohydrates

A convenient method for the syntheses of non‐1‐ynitols 8a–8d, by chemoselective addition of (trimethylsilyl)‐propargylmagnesium bromide at the anomeric center of a 1‐unprotected sugar, in the presence of 3‐C′‐halide and 3‐C′‐silyl functions in the side chain is described. In addition, an efficient method for the synthesis of 3‐C′‐hydroxymethyl sugar 3 via the addition of C₁ silyl Grignard reagents to ulose 1 and subsequent oxidation by the Fleming‐Tamao method in excellent yields is reported. Also, a suitable acid‐catalyzed isomerization of the 1,2‐O‐isopropylidene group to the 2,3‐O‐isopropylidene group (5a–5f), to get access to the anomeric center, in good to excellent yields has been depicted.     

Structural and optical properties of Na doped ZnO nanocrystalline thin films synthesized using sol–gel spin coating technique

Sodium (Na) doped Zinc oxide (ZnO) thin films have been deposited on a glass substrate by the sol–gel spin coating method. Effect of doping with various percentages of Na at a particular annealing temperature of 500 °C is studied. The samples were characterized by X-ray diffraction (XRD), micro-photoluminescence, Raman and Polarized Raman spectroscopy. The X-ray diffraction and micro-Raman spectroscopy confirmed the presence of Na substitution in zinc oxide and the wurtzite structure of the lattice is retained. An enhancement of resonant Raman scattering processes as well as longitudinal optical phonon overtones up to the fifth order were observed in the micro Raman spectra. The similar values of depolarization ratios obtained from Polarized Raman studies recommend no change in the symmetry. Photoluminescence showed a strong emission peak in the near UV at 3.2 eV and negligible visible emission.     

Development and Properties of Surfactant‐Free Water‐Dispersible Cu2ZnSnS4 Nanocrystals: A Material for Low‐Cost Photovoltaics

A simple, yet novel hydrothermal method has been developed to synthesize surfactant‐free Cu₂ZnSnS₄ nanocrystal ink in water. The environmentally friendly, 2–4 nm ultrafine particles are stable in water for several weeks. Detailed X‐ray diffraction (XRD) and high‐resolution transmission electron microscopy revealed the formation of single‐crystalline‐kesterite‐phase Cu₂ZnSnS₄. Elemental mapping by scanning electron microscopy/energy dispersive spectrometry corroborated the presence of all four elements in a stoichiometric ratio with minor sulfur deficiency. Finally, Raman spectroscopy ruled out the possible presence of impurities of ZnS, Cu₂SnS₃, SnS, SnS₂, Cu_2?xS, or Sn₂S₃, which often interfere with the XRD and optical spectra of Cu₂ZnSnS₄. X‐ray photoelectron spectroscopic studies of the as‐synthesized samples confirmed that the oxidation states of the four elements match those of the bulk sample. Optical absorption analyses of thin film and solution samples showed high absorption efficiency (>10⁴ cm^?1) across the visible and near‐infrared spectral regions and a band gap E_g of 1.75 eV for the as‐synthesized sample. A non‐ohmic asymmetric rectifying response was observed in the I–V measurement at room temperature. The nonlinearity was more pronounced for this p‐type semiconductor when the resistance was measured against temperature in the range 180–400 K, which was detected in the hot‐point probe measurement.     

Arylation of Amines and Monoarylation of Symmetrical Diamines in the Presence of Brine Solution with Diheteroaryl Halides

A simple, scalable, ligand-free, and metal-free protocol for arylation of amines and monoarylation of symmetrical diamines with diheteroaryl halides in the presence of brine solution has been developed. The protocol has broad structural applicability for chemoselective monoarylation of a wide variety of symmetrical, cyclic, and acyclic aliphatic diamines. The protocol is also applicable for selective arylation of aliphatic amine in the presence of aromatic amine.