A mild and convenient method has been developed for preparing 4,4‐dimethyloxazoline (DMOX) derivatives of fatty acids for GC–MS analysis. First, fatty acid methyl esters are converted to corresponding amides by incubation overnight at room temperature with 2‐amino‐2‐methyl‐1‐propanol and a catalytic amount of sodium methoxide. The resulting 2‐(methylpropanol) amides were isolated by partition between hexane–diethyl ether and water, and then converted to 4,4‐dimethyloxazoline derivatives by treatment with trifluoroacetic anhydride under mild conditions (50 °C for 45 min). Structures of 2‐methylpropanol amide and a DMOX derivative of oleic acid were confirmed by GC–MS. This method was applied to different FAME prepared from animal, plant or microbial lipids. The suggested method is most suitable for structure analysis of polyunsaturated fatty acids (PUFA) and for acids with double bonds in close to terminal positions. Application of the method is illustrated with spectra of the DMOX derivatives of 16:1(n‐13), 24:5(n‐6) and 24:6(n‐3) acids.

中文翻译：

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用于GC-MS的温和的多不饱和脂肪酸4,4-二甲基恶唑啉衍生物的制备方法

已经开发了一种温和便捷的方法来制备用于GC-MS分析的脂肪酸4,4-二甲基恶唑啉（DMOX）衍生物。首先，通过在室温下与2-氨基-2-甲基-1-丙醇和催化量的甲醇钠孵育过夜，将脂肪酸甲酯转化为相应的酰胺。通过在己烷-乙醚和水之间分配来分离所得的2-甲基丙醇酰胺，然后通过在温和的条件下（50°C持续45分钟）用三氟乙酸酐处理将其转化为4,4-二甲基恶唑啉衍生物。GC-MS证实了2-甲基丙醇酰胺和油酸的DMOX衍生物的结构。该方法适用于由动物，植物或微生物脂质制备的不同FAME。建议的方法最适合于多不饱和脂肪酸（PUFA）的结构分析，以及最接近末端位置具有双键的酸的分析。该方法的应用以16：1（n-13），24：5（n-6）和24：6（n-3）酸的DMOX衍生物的光谱说明。