一种用于昆虫性信息素成分单不饱和双键定位的简便方法

昆虫利用特定的性信息素成分实现种内信息交流和种间生殖隔离，性信息素成分异构体的细微差异都能导致其生物活性的很大改变。本研究利用二甲基二硫醚（DMDS）甲硫基化反应和气相色谱-电子轰击质谱（GC-EI-MS）的方法对脂肪族单不饱和醇、醛和乙酸酯类昆虫性信息素成分双键在碳链中的位置异构进行系统研究。质谱分析结果表明，含有醇和乙酸酯官能团的单不饱和烯烃甲硫基化衍生物的质谱特征碎片分子离子峰（M+）及2个主要的诊断离子m/z 61+14m ［H-（CH₂）_m-CH=S⁺ CH₃］和77+14n［CH₃S⁺ =CH（CH₂）_nOH］（或119+14n，［CH₃S⁺ =CH（CH₂）_nOOCCH₃］）丰度都很强，可以据此直接推断双键在碳链中的位置。尽管单不饱和醛类化合物DMDS衍生物的特征碎片峰也很明显，但是由于羰基的质量数和2个亚甲基的质量数相同，不能由低分辨质谱的特征碎片峰直接推断双键在碳链中的位置。DMDS甲硫基化反应结合GC-EI-MS分析方法鉴定昆虫性信息素成分单不饱和双键在碳链中的位置异构，该方法简单快捷，为昆虫性信息素的结构鉴定工作奠定了坚实的基础。

A simple method to determine the double bond position in monounsaturated insect pheromone compounds

The unique sex pheromone components were employed by insects in order to achieve their intraspecific communication and interspecific reproductive isolation. However, the trace differences in the isomers of sex pheromone components can affect their biological activity extensively. The monounsaturated pheromone components of major insect pests were methylthiolated with dimethyldisulfide (DMDS) and analyzed by capillary gas chromatography (GC)-electron impact (EI) mass spectrometry (MS) in order to determine the double bond position in the aliphatic monounsaturated chain with alcohol, aldehyde or acetate functional groups. GC-EI-MS analyses of the resulting DMDS adducts of pheromone components with alcohol or acetate functional groups showed simple mass spectra with recognizable molecular ions and two high intensity diagnostic ions at m/z 61+14m ［H-(CH₂)_m-CH=S⁺ CH₃］ and 77+14n［CH₃S⁺ =CH(CH₂)_nOH］(or 119+14n，［CH₃S⁺ =CH(CH₂)_nOOCCH₃］)indicating the original double bond position in the aliphatic chain. Although the DMDS adducts of monounsaturated aldehydes also produced the molecular ions of the derivatives and a series of key fragment ions, this can not allow an immediate determination of the position of the double bond in the original unsaturated compounds by low-resolution EI-MS since the nominal mass of a carbonyl group is the same as that of two methylene groups. The location of the double-bond position using the DMDS adducts and GC-EI-MS methods is simple, time efficient, and highly sensitive, and this procedure shows a good prospect in sex-pheromone identification.