Dispersal-induced pattern-forming instabilities in host–parasitoid metapopulations

Nonlinear Dynamics - Dispersal-induced pattern formation is important from both fundamental and application points of view. Spatial pattern in an ecological system can strongly depend on exogenous...     

Cobalt(III)‐Catalyzed Intramolecular Cross‐Dehydrogenative C−H/X−H Coupling: Efficient Synthesis of Indoles and Benzofurans

An efficient cobalt(III)‐catalyzed intramolecular cross‐dehydrogenative C?H/N?H coupling of ortho‐alkenylanilines has been developed utilizing O₂ as a terminal oxidant. The developed reaction tolerates various reactive functional groups and allows the synthesis of diverse indole derivatives in good to excellent yields. The method was successfully extended to the synthesis of benzofurans through the intramolecular cross‐dehydrogenative C?H/O?H coupling of ortho‐alkenylphenols.     

Kinetic Analysis, Expression Pattern, and Production of a Recombinant Fungal Protease Inhibitor of Tasar Silkworm Antheraea mylitta

Antheraea mylitta, a tasar silk-producing insect of Saturniidae family, expresses a fungal protease inhibitor named as A. mylitta fungal protease inhibitor-1 (AmFPI-1). AmFPI-1 inhibits alkaline protease of Aspergillus oryzae but its mechanism of action is not known. To understand the mode of inhibition of AmFPI-1 against the fungal protease, it was purified from the hemolymph of A. mylitta larvae and inhibitory activity against A. oryzae protease was studied. Kinetic analysis of purified AmFPI-1 on alkaline protease of A. oryzae showed that AmFPI-1 acts as a canonical-type competitive inhibitor with equilibrium dissociation constant (K _i ) of 60?nM. Expression of AmFPI-1 in different body tissues of fifth instar A. mylitta larvae was determined by real-time PCR, and the highest expression was observed in fat body followed by integument, silk gland, and gut, indicating that AmFPI-1 has pleiotropic functions including protection from invading fungi. The cDNA of AmFPI-1 was expressed in Escherichia coli, and recombinant His-tagged fusion protein was purified by Ni-NTA chromatography. Recombinant AmFPI-1 showed inhibitory activity against A. oryzae protease and suggested its use in various biological applications to prevent proteolysis.     

Syntheses of chiral β- and γ-amino ethers, morpholines, and their homologues via nucleophilic ring-opening of chiral activated aziridines and azetidines

Lewis acid catalyzed quaternary ammonium salt mediated highly regioselective ring-opening of chiral activated aziridines and azetidines with alcohols to nonracemic β- and γ-amino ethers has been developed. The reaction mainly proceeds via an S(N)2 pathway, and the partial racemization of the starting substrate was effectively controlled by using quaternary ammonium salts. β- and γ-amino ethers are obtained with high enantio- and diastereospecificity (ee up to >99%, de up to 99%). The methodology was further extended to synthesize morpholines and their homologues with high enantiospecificity (ee up to 90%) when halo alcohols were employed as the nucleophiles.     

One-pot synthesis of pyrano[4,3-b]quinolinones from 2-alkynyl-3-formylquinolines via oxidative 6-endo-dig ring closure

A new regioselective one-pot procedure to synthesize pyranoquinolinones from readily available 2-alkynyl 3-formylquinolines under mild NaClO₂/H₂O₂ conditions in good yields has been explored. This reaction sequence, involving oxidation followed by regioselective electrophilic 6-endo-dig cyclization is more efficient over the traditional Pd(0)-mediated synthesis. When scavenger-free conditions were used, unusual chlorinated furoquinolinone derivatives were obtained.     

Organocatalysis in water at room temperature with in-flask catalyst recycling

A new designer surfactant is described containing a covalently bound organocatalyst, proline. This species is water-soluble and, via spontaneous nanomicelle formation, catalyzes aldol reactions on water-soluble or -insoluble substrates in water as the only medium. Recycling the catalyst is trivial, as the amphiphile/catalyst remains in the aqueous phase in the flask.     

Mononuclear, helical binuclear palladium and lithium complexes bearing a new pyrrole-based NNN-pincer ligand: fluxional property

A new pyrrole based NNN-pincer ligand, 2,5-bis(3,5-dimethylpyrazolylmethyl)pyrrole 2, was readily synthesized in two steps from pyrrole in 56% yield. The lithiation of the pincer ligand 2 using n-BuLi led to isolation of the dimeric lithium complex, [Li{μ-C(4)H(2)N-2,5-(CH(2)Me(2)pz)(2)-N,N,N}](2) 4, in 23% crystalline yield. The transmetalation reaction of 4 with [Pd(PhCN)(2)Cl(2)] afforded the mononuclear Pd(II) complex, [PdCl{C(4)H(2)N-2,5-(CH(2)Me(2)pz)(2)-N,N,N}] 5, containing one chloride ion in 45% yield. Alternatively 5 was obtained in an excellent yield of 87% by the reaction 2 of with [Pd(COD)Cl(2)] in the presence of triethylamine. On the contrary, a 20-membered macrometalacyclic molecule, [Pd(2)Cl(4){μ-C(4)H(3)N-2,5-(CH(2)Me(2)pz)(2)-N,N}(2)] 6, in which two PdCl(2) units are bridged by two molecules of 2 to give a helical structure, was synthesized by the reaction of 2 with [Pd(COD)Cl(2)] in the absence of base. The acetate analogue of complex 5, [Pd(OAc){C(4)H(2)N-2,5-(CH(2)Me(2)pz)(2)-N,N,N}] 3, was obtained by the treatment of 2 with [Pd(OAc)(2)]. The pyrrole twist angle of 5 is higher than that of 3. Complexes 3 and 5 show an AB pattern for their methylene protons at room temperature in CDCl(3) as well as in DMSO-d(6). The variable temperature NMR studies showed that the acetate and chloride complexes exhibit slightly different coalescence temperatures, which is a solvent dependent phenomenon, and twist angles.     

Insights into Cobalta(III/IV/II)‐Electrocatalysis: Oxidation‐Induced Reductive Elimination for Twofold C−H Activation

The merger of cobalt‐catalyzed C?H activation and electrosynthesis provides new avenues for resource‐economical molecular syntheses, unfortunately their reaction mechanisms remain poorly understood. Herein, we report the identification and full characterization of electrochemically generated high‐valent cobalt(III/IV) complexes as crucial intermediates in electrochemical cobalt‐catalyzed C?H oxygenations. Detailed mechanistic studies provided support for an oxidatively‐induced reductive elimination via highly‐reactive cobalt(IV) intermediates. These key insights set the stage for unprecedented cobaltaelectro two‐fold C?H/C?H activation.