Investigation of variability in the matrix effect on stable isotope-labeled internal standards in liquid chromatography-tandem mass spectrometry analysis of 25 pesticides in vegetables.

The matrix effects (ME) in simultaneous analysis of pesticide residue using liquid chromatography-tandem mass spectrometry (LC-MS/MS) were evaluated by comparing the slopes of matrix-matched and reagent-only calibrations of four types of vegetable samples. Both the sampling and measurement variances of the ME were also determined using one-way analysis of variance. Substantial ion suppression (ME<-20%) was observed in komatsuna, spinach, and tomato when a modified Japanese official method was implemented.

The structure-activity relationship of aryloxyacetylthioureas for the inhibition of radicle elongation.

Orobanchaceae root parasitic weeds cause significant damage to agriculture and become threats to global food security. Integrated pest management is a key concept in modern agriculture and requires chemicals with various modes of action. Planteose accumulates as a storage carbohydrate in the dry seeds of root parasitic weeds.

Access to γ-Carbolines: Synthesis of Isocryptolepine.

A new method to synthesize γ-carboline derivatives has been developed starting from 3,5-dibromo-4-pyridinamine by monoarylation using the Suzuki-Miyaura cross-coupling reaction followed by the base-mediated ring closure to pyrrole formation. Synthesis of a series of γ-carboline derivations from the 4-brominated γ-carboline has been achieved by employing various coupling reactions and N-alkylations. This method has been applied for the synthesis of the antimalarial and anticancer natural product isocryptolepine.

Furan- and Thiophene-2-Carbonyl Amino Acid Derivatives Activate Hypoxia-Inducible Factor via Inhibition of Factor Inhibiting Hypoxia-Inducible Factor-1.

Induction of a series of anti-hypoxic proteins protects cells during exposure to hypoxic conditions. Hypoxia-inducible factor-α (HIF-α) is a major transcription factor that orchestrates this protective effect. To activate HIF exogenously, without exposing cells to hypoxic conditions, many small-molecule inhibitors targeting prolyl hydroxylase domain-containing protein have been developed.

Palladium-Catalyzed Cyanothiolation of Internal Alkynes Using Organic Disulfides and tert-Butyl Isocyanide.

Despite the availability of selective synthetic approaches to multifunctionalized substituted olefins, the cyanothiolation of internal alkynes has been much less explored. Herein, we show that nonactivated internal alkynes can be successfully cyanothiolated with diaryl disulfides and tert-butyl isocyanide in the presence of a Pd catalyst (e.g.

A Benzoyl Peroxide/Diphenyl Diselenide Binary System for Functionalization of Alkynes Leading to Alkenyl and Alkynyl Selenides.

Binary systems consisting of benzoyl peroxide (BPO) and diorganyl diselenide are effective in the selective benzoyloxyselenation of internal alkynes to afford the corresponding β-(benzoyloxy)alkenyl selenides in good yields. In contrast to internal alkynes, terminal alkynes undergo a novel C(sp)-H substitution with the phenylseleno group of the BPO/(PhSe) system, providing alkynyl selenides in good yields. Both selenation reactions might proceed via benzoyloxy selenide (PhC(O)O-SeAr) as a key intermediate for electrophilic addition to alkynes.

Sequential Synthesis, Olfactory Properties, and Biological Activity of Quinoxaline Derivatives.

A simple, practical, and rapid access to quinoxalin-2-ones , 1,2,3,4-tetrahydroquinoxalines , quinoxalines , and quinoxalin-2(1)-ones has been achieved, based on the copper-catalyzed quinoxalinone formation of 2-haloanilines and amino acids followed by their reduction and oxidation. The olfactory properties and lipid accumulation inhibitory activity in cultured hepatocytes of the quinoxaline derivatives were also evaluated.

A facile and rapid access to resveratrol derivatives and their radioprotective activity.

A facile and rapid access to resveratrol derivatives has been achieved based on palladium-catalyzed oxidative Heck reaction of aryl boronic acids with styrenes followed by demethylation in moderate to good yields. A series of resveratrol derivatives with various functional groups has been synthesized easily. The radioprotective activity of synthesized compounds has also been evaluated using rat thymocytes.

Proline-Mediated Transition Metal-Free Access to 1H-Indazolones from 2-Halobenzohydrazides.

Transition metal-free access to 1H-indazolones 1 has been achieved on the basis of base-mediated intramolecular C-N bond formation. Reactions of 2-halobenzohydrazides 2 with potassium tert-butoxide in the presence of catalytic proline provided indazolones 1 in moderate to good yields. This transformation may proceed primarily via the radical pathway according to the control experiment with a radical scavenger.

Highly regioselective simultaneous introduction of phosphino and seleno groups into unsaturated bonds by the novel combination of (Ph2P)2 and (PhSe)2 upon photoirradiation.

A novel combination of tetraphenyldiphosphine and diphenyl diselenide under photoirradiation conditions attains simultaneous introduction of diphenylphosphino and phenylseleno groups into carbon-carbon unsaturated bonds such as terminal alkynes or allenes, regioselectively.

Donors and acceptors based on triangular dehydrobenzo[12]annulenes: formation of a triple-layered rosette structure by a charge-transfer complex.

We present here the results of studies of the synthesis and properties of donors and acceptors based on triangular dehydrobenzo[12]annulene ([12]DBA) system as a pi core. These studies were aimed at controlling the supramolecular crystal structure. Toward this end, the tricyano[12]DBA 2 and dodecafluoro[12]DBA ( 3) were synthesized as acceptors (A) and the tris(dialkylamino)[12]DBAs 4a-d as donors (D), and their electronic properties were determined by electronic absorption spectroscopy and electrochemical measurements.

A highly regioselective palladium-catalyzed hydrophosphination of alkynes using a diphosphine-hydrosilane binary system.

A novel transition-metal-catalyzed hydrophosphination of terminal alkynes using a diphosphine-hydrosilane binary system takes place regioselectively to provide vinylic phosphines, which undergo air oxidation during workup, affording the corresponding vinylphosphine oxides in good yields. In this hydrophosphination, hydrosilanes act as a useful hydrogen source, and furthermore, small amounts of oxygen is required to accomplish the reaction efficiently.

Site-selective guest inclusion in molecular networks of butadiyne-bridged pyridino and benzeno square macrocycles on a surface.

We present here the formation of a modular 2D molecular network composed of two different types of square-shaped butadiyne-bridged macrocycles, having intrinsic molecular voids, aligned alternately at the solid-liquid interface. Site-selective inclusion of a guest cation took place at every other molecular void in the molecular network with two different recognition sites.

Two-photon absorption properties of Dehydrobenzo[12]annulenes and hexakis(phenylethynyl)benzenes: effect of edge-linkage.

Two-photon absorption (TPA) properties of two trefoil-shaped compounds with different edge linkages--tris(hexadehydrotribenzo[12]annulene) and tris(tetradehydrotribenzo[12]annulene)--and three asterisk-shaped compounds having no edge-linkage--hexakis(phenylethynyl)benzenes--are investigated experimentally by the open-aperture Z-scan and TPA-induced fluorescence methods with wavelength tuneable femtosecond pulses. The compound with ethynylene edge-linkage exhibits the most intense TPA (the maximal TPA cross section is 1300+/-170 GM at 572 nm where 1 GM=10(-50) cm(4) s molecule(-1) photon(-1)). The TPA activity of the compounds is primarily explained in terms of the planarity of the molecules in relation with the type of edge-linkage.

Synthesis of dehydrobenzo[18]annulene derivatives and formation of self-assembled monolayers: implications of core size on alkyl chain interdigitation.

The synthesis of a series of dodecadehydrotribenzo[18]annulene ([18]DBA) derivatives is reported, together with their steady-state absorption and fluorescence properties. The main focus, though, is on the self-assembly of these compounds at the liquid-solid interface as investigated with scanning tunneling microscopy (STM), highlighting the effect of alkyl chain orientation and alkyl chain length on the molecular ordering. Owing to the large triangular pi-electron system of the [18]DBAs, two different types of alkyl chain orientation are observed.

Theoretical studies on graphyne substructures: geometry, aromaticity, and electronic properties of the multiply fused dehydrobenzo[12]annulenes.

The geometries of multiply fused dehydrobenzo[12]annulenes [12]DBAs 2-7 with various topologies, which are considered as graphyne fragments, have been optimized at the B3LYP/6-31G* level of theory. Most of the optimized geometries of fused DBAs have planar structures excluding a boomerang-shaped bisDBA 4, a trefoil-shaped trisDBA 6, and a wheel-shaped DBA 7. For the boomerang-shaped bisDBA 4 and the trefoil-shaped trisDBA 6, distortions originate from the steric repulsion between hydrogen atoms attached to adjacent benzene rings.

Two-dimensional porous molecular networks of dehydrobenzo[12]annulene derivatives via alkyl chain interdigitation.

The self-assembly of a series of hexadehydrotribenzo[12]annulene (DBA) derivatives has been scrutinized by scanning tunneling microscopy (STM) at the liquid-solid interface. First, the influence of core symmetry on the network structure was investigated by comparing the two-dimensional (2D) ordering of rhombic bisDBA 1a and triangular DBA 2a (Figure 1). BisDBA 1a forms a Kagomé network upon physisorption from 1,2,4-trichlorobenzene (TCB) onto highly oriented pyrolytic graphite (HOPG).

Synthesis and properties of trefoil-shaped tris(hexadehydrotribenzo[12]annulene) and tris(tetradehydrotribenzo[12]annulene).

[reaction: see text] Trefoil-shaped tris(hexadehydrotribenzo[12]annulene) possessing a substructure of the ultimate two-dimensional C(sp)-C(sp(2)) network, graphyne, and the related tris(tetradehydrotribenzo[12]annulene) were synthesized, and their ground- and excited-state properties were investigated.

Molecular geometry directed Kagomé and honeycomb networks: toward two-dimensional crystal engineering.

We present here the formation of a molecular Kagomé network within a two-dimensional (2D) crystal on a surface. This system provides a clear example of how, by design, molecular geometry can be expressed at the level of the 2D crystal lattice, leading to the formation of open networks. Key elements to control molecular network formation are core symmetry, location and orientation of interacting and connecting substituents, as well as symmetry matching between the networks and the surface.

Novel synthesis of bridged phenylthienylethenes and dithienylethenes via Pd-catalyzed double-cyclization reactions of diarylhexadienynes.

[reaction: see text] Bridged phenylthienylethenes and dithienylethenes were synthesized via Pd-catalyzed double-cyclization reactions of (Z,Z)-1,6-diaryl-1,5-hexadien-3-ynes. Pd-catalyzed as well as photoinduced Z/E isomerization of the products were also investigated.