Stereoselective synthesis of (2S,3S,7S)-3,7-dimethylpentadec-2-yl acetate and propionate, the sex pheromones of pine sawflies

The stereoselective synthesis of (2S,3S,7S)-3,7-dimethylpentadec-2-yl acetate (2) and propionate (3) was accomplished by utilizing the cheap and easily available chiron (R)-4-methyl-δ-valerolactone (4). The key steps were chelation-controlled addition of Gilmann reagent to chiral β-alkoxy aldehyde 12 and the Cu(I)-catalyzed coupling of Grignard reagent with bromoester 5 in the presence of NMP.     

Analysis of chemical profiles of insect adhesion secretions by gas chromatography–mass spectrometry

This article reports on the chemical analysis of molecular profiles of tarsal secretions of the desert locust Schistocerca gregaria (Forsskål, 1775) by gas chromatography hyphenated with quadrupol mass spectrometry (GC–MS) as well as ¹H-nuclear magnetic resonance (¹H NMR) spectroscopy. Special focus of this study was to elaborate on sampling methods which enable selective microscale extraction of insect secretions in a spatially controlled manner, in particular tarsal adhesive secretions and secretions located on cuticle surfaces at the tibia. Various solvent sampling procedures and contact solid-phase microextraction (SPME) methods were compared in terms of comprehensiveness and extraction efficiencies as measured by signal intensities in GC–MS. Solvent sampling with water as extraction solvent gave access to the elucidation of chemical profiles of polar compound classes such as amino acids and carbohydrates, but is extremely tedious. Contact SPME on the other hand can be regarded as a simplified and more elegant alternative, in particular for the lipophilic compound fraction. Many proteinogenic amino acids and ornithine as well as carbohydrate monomers arabinose, xylose, glucose, and galactose were detected in tarsal secretions after acid hydrolysis of aqueous extracts. Qualitatively similar but quantitatively significantly different molecular profiles were found for the lipid fraction which contained mainly n-alkanes and internally branched monomethyl-, dimethyl-, and trimethyl-alkanes in the C23–C49 range as well as long chain fatty acids and aldehydes. Especially, hydrocarbons with >C40 carbon numbers have previously been rarely reported for insect secretions. The results suggest that the investigated insect secretions are complex emulsions which allow the attachment of tarsi on various otherwise incompatible materials of smooth and rough surfaces. The solid consistence of the established alkanes at ambient temperatures might contribute to a semi-solid consistence of the adhesive, amalgamating partly opposing functions such as slip resistance, tarsal release, desiccation resistance, and mechanical compliance. The methods developed can be extended to other similar applications of studying compositions of insect secretions of other species.     

比较分析黔产虫茶矿质元素及氨基酸含量

测定贵州不同产地虫茶的微量元素和游离氨基酸含量,了解其变化规律;矿质元素采用原子吸收光谱和分光光度法测定,氨基酸采用氨基酸自动分析仪测定。黔产虫茶C a元素含量最高,为5687m g/kg,Cu含量最低,为13m g/kg,丝氨酸含量最高,为516m g/100g,蛋氨酸含量最低,为46m g/100g,不同产地虫茶矿质元素和游离氨基酸含量变化差异大,相对标准偏差在0.1691—0.6903之间。黔产虫茶矿质元素和游离氨基酸含量体现较好品质,但含量差异大。     

HG-AFS同时测定驱蚊水中的砷和汞

采用氢化物发生-原子荧光光谱法测定驱蚊水中的砷(A s)和汞(Hg)。在0—50.0μg/L范围内砷和汞的浓度与荧光强度呈线性关系,相关系数均为0.9993,加标回收率分别达到99.76%—103.46%和90.10%—100.10%,砷、汞测定结果的RSD分别小于3.9%和6.6%;同时指出了测定时应注意的事项。     

Fluorine in pheromones: Synthesis of fluorinated 12-dodecanolides as emerald ash borer pheromone mimetics

A series of five 12-dodecanolides have been synthesised containing CF₂ groups at C5, C6, C7, C8 and in one case, a double substitution at C5 & C8, as a strategy to bias the conformational space accessed by these macrocycles, and to assess if the analogues may act as mimetics of 13-membered macrolide pheromones associated with the emerald ash borer. Accordingly individual syntheses of 5,5-difluoro- 5, 6,6-difluoro- 6, 7,7-difluoro- 7, 8,8-difluoro- 8 and 5,5,8,8-tetrafluoro- 9, 12-dodecanolides are outlined, and X-ray structural data were obtained for three (5, 8 and 9) of these compounds. The structures show clearly that the CF₂ groups occupy ‘corner’ locations in the macrocycle consistent with their ability to bias accessible conformations. The fluorine containing 12-dodecanolides all generated an electro-antennogram response in female beetles.     

Monitoring insect pest infestation via different spectroscopic techniques

Nowadays, monitoring and observing insect pest populations is a major and crucial issue in agriculture, especially for crop protection. Spectroscopic techniques are well recognized for detecting and monitoring insect pests in the field and also the internal quality of fruit. There are several spectroscopic techniques with specific characteristic features, including mass spectrometry, ultraviolet–visible spectroscopy, infrared spectroscopy, and nuclear resonance spectroscopy. Nevertheless, limitations and complexity are the constraints of these technologies. In this paper, the spectroscopic and imaging spectroscopic techniques are discussed, compared, and investigated, namely fluorescence light detection and ranging (LIDAR) to study the fluorescence of diverse types of planthopper (Hemiptera) and moth (Lepidoptera), visible and near-infrared (Vis/NIR) spectroscopy to detect internal insect-infested jujubes, NIR spectroscopy to determine spectral properties of oil palm bagworms, hyperspectral transmittance image for detecting insect-damaged vegetable soybeans, and remote sensing measurement to detect bagworm infestation in oil palm plantations. These techniques are found to be reliable methods for better monitoring of insect pest movement in the harvested plant and in the ground, for the detection of insect-damaged vegetable soybeans and internal insect infestation in jujubes, and for the determination of oil palm bagworm spectral properties.     

Numerical Study of Two-Winged Insect Hovering Flight

The two-winged insect hovering flight is investigated numerically using the lattice Boltzmann method (LBM). A virtual model of two elliptic foils with flapping motion is used to study the aerodynamic performance of the insect hovering flight with and without the effect of ground surface. Systematic studies have been carried out by changing some parameters of the wing kinematics, including the stroke amplitude, attack angle, and the Reynolds number for the insect hovering flight without ground effect, as well as the distance between the flapping foils and the ground surface when the ground effect is considered. The influence of the wing kinematic parameters and the effect of the ground surface on the unsteady forces and vortical structures are analyzed. The unsteady forces acting on the flapping foils are verified to be closely associated with the time evolution of the vortex structures, foil translational and rotational accelerations, and interaction between the flapping foils and the existed vortical flow. Typical unsteady mechanisms of lift production are identified by examining the vortical structures around the flapping foils. The results obtained in this study provide some physical insight into the understanding of the aerodynamics and flow structures for the insect hovering flight.     

复凝聚法制备昆虫激素模拟物十二醇微胶囊及其释放性能

以明胶(GE)和阿拉伯胶(AG)为壁材, 通过复凝聚法将昆虫激素模拟物十二醇(C12OH)包覆在微胶囊中, 改变微胶囊壁材的浓度和交联度, 探讨了体系中C12OH的可控释放性能. 通过对壁材质量比为1及不同pH条件下的壁材凝聚率测试确定最佳复凝聚的pH为4.0; 考察了不同分散剂对微胶囊及其分散液性能的影响, 确定以Tween 20/Span 80(质量比1∶1)作为复凝聚法包覆C12OH体系的分散剂. 在壁材质量分数大于或等于3%条件下制备的微胶囊粒径大于壁材质量分数为2%的微胶囊, 胶囊的载药量和C12OH包覆率明显高于后者. 增加交联剂的用量, 壁材交联度、胶囊的载药量和C12OH包覆率都显著提高. 在相同用量的情况下, 用甲醛作交联剂时得到的微胶囊的交联度比用戊二醛作交联剂时的要低, 但其对C12OH的包覆率更高. 通过扫描电镜对微胶囊进行了分析, 认为GE与AG通过复凝聚能够将C12OH包覆在微胶囊内部. 对胶囊中C12OH在恒温恒湿条件下的释放研究结果表明, 3%与4%壁材含量下1%戊二醛交联的微胶囊和5%壁材含量下4%戊二醛交联的微胶囊中C12OH的释放行为有明显的可控性. 通过调节微胶囊的壁材含量和交联度可以达到昆虫激素可控释放的目的.     

Isolation of novel azadirachtins H and I by high-performance liquid chromatography

Summary A high-performance liquid chromatographic procedure for the isolation of azadirachtins A, B, D, H and I is described. While azadirachtins A, B, and D are already known, azadirachtins H and I have been isolated for the first time from neem kernels.