The geometric isomers of methyl-2,4,6-decatrienoate, including pheromones of at least two species of stink bugs

All eight geometric isomers of methyl 2,4,6-decatrienoate were synthesized from readily accessible starting materials by fully exploiting Wittig-type olefinations, and taking advantage of an easy separation of 2E and 2Z unsaturated esters. The aggregation pheromone of the brown-winged green bug, Plautia stali, methyl (E,E,Z)-2,4,6-decatrienoate (also a cross-attractant for the brown marmorated stink bug, Halyomorpha halys), was expediently produced in two easy steps from (E)-4,4-dimethoxy-2-butenal in 55% yield. The sex pheromone of the red-shouldered stink bug, Thyanta pallidovirens, methyl (E,Z,Z)-2,4,6-decatrienoate, was conveniently synthesized from 2,4-octadiyn-1-ol in 32% yield using in situ manganese dioxide oxidation-Wittig condensation in a key step.     

A facile one-pot stereoselective synthesis of trisubstituted (E)-2-methylalk-2-enoic acids from unactivated Baylis-Hillman adducts and a simple access to some important insect pheromones

An efficient one-pot stereoselective synthesis of trisubstituted (E)-2-methylalk-2-enoic acids has been accomplished by treatment of unactivated Baylis-Hillman adducts, 3-hydroxy-2-methylenealkanoates, with Al-NiCl₂·6H₂O in methanol at room temperature followed by hydrolysis. The method has been applied to the synthesis of three important insect pheromones, (4S,2E)-2,4-dimethyl-2-hexenoic acid, (+)-(S)-manicone and (+)-(S)-normanicone.     

Unsymmetrical double Wittig olefination on the syntheses of insect pheromones. Part 1: Synthesis of 5,9-dimethylpentadecane, the sexual pheromone of Leucoptera coffeella

An expeditious three-step synthesis of a mixture of stereoisomers of 5,9-dimethylpentadecane 1, the sexual pheromone of the coffee leaf miner Leucoptera coffeella, is described. The route employs an unsymmetrical double Wittig olefination to build the carbon skeleton of the molecule, as the key reaction. The bis-phosphonium salt 3, derived from 1,3-dibromopropane 2, reacted ‘one-pot’ with the ketones 2-octanone and 2-hexanone, affording the asymmetric diene 4. This was readily hydrogenated over Pd/C, furnishing pheromone 1 in 54% overall yield. Synthetic 1 showed high biological activity when tested in field experiments.     

Radical mediated stereoselective synthesis of meso-7,11-dimethylheptadecane, a female sex pheromone component of the spring hemlock looper and the pitch pine looper

meso-7,11-Dimethylheptadecane, a female sex pheromone component of the spring hemlock looper and the pitch pine looper, was synthesized from ethyl 2-(bromomethyl)propenoate in nine steps and 14% overall yield. The key step in the synthesis is the highly diastereoselective chelation-controlled radical reaction of diethyl 4-benzyloxy-2,6-dimethyleneheptanedioate with pentyl iodide performed in the presence of 6 equiv of MgBr₂·OEt₂.     

用异戊二烯的催化调聚反应合成梨圆蚧性信息素组份

梨圆蚧Quadraspidiotus perniciosus是世界性的农业害虫,主要危害苹果、梨树等果树.Gieselmann和Anderson等分离并鉴定出梨圆蚧性信息素为3,7-二甲基-2,7-辛二烯-1-醇丙酸酯(1)和7-甲基-3-亚甲基-7-辛二烯-1-醇丙酸酯(2).1的Z体和E体的比例约为10:1.田间生测发现.1的Z体、E体对雄性蚧虫均有强烈的引诱活性,两者以不同比例混合使用,活性并无明显的降低.     

基于蚁群算法的景象匹配定位

景象匹配定位是精确制导的重要技术,通过对景象匹配定位和蚁群算法的研究,提出一种基于蚁群算法的匹配定位方法,蚁群算法具有快速全局寻优能力,应用蚁群算法计算模版图像在基准图像中的匹配位置,根据匹配定位参数的特点,建立二维的蚁群搜索空间,定义图像的归一化积相关作为相似性度量并更新蚁群的信息素,利用信息素及启发信息来计算状态转移概率,蚁群最终聚集到适应度函数最大的路径上。实验结果表明：蚁群算法可以准确有效地估计匹配位置。