Synthesis of heterocycle appended spiro(oxindole-3,2’-pyrrolidine) derivatives from heterocyclic ylidenes and azomethine ylide through 1,3-dipolar cycloaddition reactions

Spiro(oxindole-3,2’-pyrrolidine) is a privileged scaffold displaying a wide spectrum of biological activities. A series of these molecules containing heterocyclic rings attached to the pyrrolidine unit has been synthesized utilizing the classical 1,3-dipolar cycloaddition reaction of azomethine ylide with heterocyclic ylidenes. The method portrays a two-step functionalization of thiophene/furan with spiropyrrolidine oxindoles in the second/third positions. Biological activity evaluation for antibacterial, cell toxicity, and anticancer potential were done. Compounds exhibited no antibacterial activity. However, they were found to be non-cytotoxic upto 100?µg/ml and to exhibit potent anticancer activity by activating pro-apoptotic genes p53 and caspase 7.     

Expeditious and Divergent Total Syntheses of Aspidosperma Alkaloids Exploiting Iridium(I)‐Catalyzed Generation of Reactive Enamine Intermediates

A new approach for the divergent total syntheses of (±)‐vincaminorine, (±)‐N‐methylquebrachamine, (±)‐quebrachamine, (±)‐minovine and (±)‐vincadifformine, each in less than 10 linear steps starting from a single δ‐lactam building block, is reported. Key to our route design is the late‐stage generation of reactive enamine functionality from stable indole‐linked δ‐lactams via a highly chemoselective iridium(I)‐catalyzed reduction. The efficiently formed secodine intermediates subsequently undergo either a formal Diels–Alder cycloaddition or a competitive Michael addition/reduction to access aspidosperma‐type alkaloids in excellent diastereoselectivities. Product selectivity could be controlled by changing the indole N‐protecting group in the reductive cyclization precursors. An asymmetric variant of this synthetic strategy for the synthesis of (+)‐20‐epi‐ibophyllidine is also described.     

Laccase‐Catalyzed Synthesis of Low‐Molecular‐Weight Lignin‐Like Oligomers and their Application as UV‐Blocking Materials

The laccase‐catalyzed oxidative polymerization of monomeric and dimeric lignin model compounds was carried out with oxygen as the oxidant in aqueous medium. The oligomers were characterized by using gel permeation chromatography (GPC) and matrix‐assisted laser desorption ionization time‐of‐flight mass spectroscopy (MALDI‐TOF MS) analysis. Oxidative polymerization led to the formation of oligomeric species with a number‐average molecular weight (M_n) that ranged from 700 to 2300 Da with a low polydispersity index. Spectroscopic analysis provided insight into the possible modes of linkages present in the oligomers, and the oligomerization is likely to proceed through the formation of C?C linkages between phenolic aromatic rings. The oligomers were found to show good UV light absorption characteristics with high molar extinction coefficient (5000–38 000 m ^?1 cm^?1) in the UV spectral region. The oligomers were blended independently with polyvinyl chloride (PVC) by using solution blending to evaluate the compatibility and UV protection ability of the oligomers. The UV/Vis transmittance spectra of the oligomer‐embedded PVC films indicated that these lignin‐like oligomers possessed a notable ability to block UV light. In particular, oligomers obtained from vanillyl alcohol and the dimeric lignin model were found to show good photostability in accelerated UV weathering experiments. The UV‐blocking characteristics and photostability were finally compared with the commercial low‐molecular‐weight UV stabilizer 2,4‐dihydroxybenzophenone.     

Asymmetric organocatalysis

The field of asymmetric organocatalysis is rapidly developing and attracts an increasing number of research groups around the world. Here we present a brief overview of this area, guided by a mechanistic classification. Accordingly, organocatalysts are categorized as either Lewis base, Lewis acid, Br?nsted base, or Br?nsted acid catalysts.     

Chemical composition,antioxidant and antiproliferative activities of essential oil from rhizome and leaves of Curcuma mutabilis Škorničk., M. Sabu & Prasanthk., endemic to Western Ghats of India

Abstract

Hydro-distilled essential oils, from fresh rhizomes and leaves of Curcuma mutabilis ?korni?k., M.Sabu & Prasanthk., characterized by GC–MS revealed the presence of thirty three and twenty three compounds therein respectively. Whilst estrone methyl ether (3-Methoxyestra-1,3,5(10)-trien-17-one) was the major component in rhizome oil (47.35%), sesquiterpene hydrocarbons predominated as the major group (63.92%) in leaf oil with a higher preponderance of β-caryophyllene (25.48%), β-farnesene (19.47%) and α-humulene (11.01%). Weak antioxidant activities observed in these oils determined by DPPH and ABTS methods were apparently influenced both by the oil composition and the assay conditions. Rhizome oil showed higher antiproliferative activity than leaf oil against leukemic K562 (IC₅₀-6.8µg/mL) and colorectal HCT116 (IC₅₀-8.5µg/mL) cancer cell lines. This first report reveals composition and biological activities of essential oils from C. mutabilis.     

N-heterocyclic carbene (NHC)-catalyzed direct amidation of aldehydes with nitroso compounds

NHC-catalyzed direct amidation of aldehydes with nitroso compounds is a powerful method for the synthesis of N-arylhydroxamic acids. A variety of aryl, alkyl, alkenyl, and heterocyclic aldehydes were found to give excellent yields of the corresponding N-arylhydroxamic acids. This chemistry was also extended to the synthesis of chiral N-arylhydroxamic acids by kinetic resolution of alpha-branched aldehydes, a domino amidation-redox amination reaction of acrolein, and a three-component reaction for the synthesis of N-arylaziridines.     

An 80 Gbps multi-band access radio over fiber link with single side band optical millimeter-wave dispersion-tolerant transmission without FBG and optical filter

We are presenting a new low-cost Single Sideband (SSB) modulated Radio-over Fiber (RoF) communication system for millimeter (mm)-wave multiband wireless communication at the frequencies of 40 GHz, 80 GHz and 120 GHz. Its principle lies in the Carrier Suppressed modulation through a nested dual electrode Mach–Zehnder Modulator (MZM) and product modulator based baseband signal decomposition. In this novel method, the optical signal is decomposed into different SSB signals using a power splitter and product modulators at the base station. This proposed method uses a different technique for a baseband signal decomposition from the existing method. The proposed signal decomposition technique has reduced the nonlinearities due to the FBGs. The proposed method is compared with the existing method in terms of BER, data rate and OSNR. The simulation results disclose that our proposed scheme outperforms the existing methods at a higher data rate of 80 Gbps with a minimum BER and privileged Q factor.     

On the Lie Symmetry,Conservation Laws and Painlevé Analysis for the Viscous Transonic Equation

The properties of the nonlinear viscous transonic equation is analysed in detail. The Painlevé test shows that it is not completely integrable. The equation does not reduce to a member of Painlevé class by any similarity transformation of variables.