The three isomeric components of the San Jose scale pheromone, 5–7, have been synthesized from a common β-keto ester intermediate. A study of the alkylation of the dianion of methyl acetoacetate with a series of alkylating agents with the same carbon skeleton has been carried out. The trisubstituted alkenes in 5 and 6 have been synthesized stereospecifically via a copper-catalyzed coupling of a methyl Grignard reagent with the E or Z enol phosphate from the alkylated β-keto ester. In the case of the Z enol derivative, the coupling reaction was carried out on the diethyl- and diphenylphosphates, and the enol triflate. The diethyl enol phosphate gave the highest stereoselectivity. The synthetic pheromones were attractive to San Jose scale in the field.[Formula: see text]
三种同分异构体是从共同的β-酮酸酯中间体合成的。对甲基乙酰乙酸酯的二负离子进行烷基化研究,使用具有相同碳骨架的一系列烷基化试剂。通过铜催化的甲基格氏试剂与烷化的β-酮酸酯的E或Z烯醇磷酸酯的偶联,立体特异地合成了5和6中的三取代烯烃。在Z烯醇衍生物的情况下,偶联反应在二乙基磷酸酯、二苯基磷酸酯和烯醇三氟乙酸酯上进行。二乙基烯醇磷酸酯具有最高的立体选择性。合成的信息素在野外对圣何塞鳞虫具有吸引力。