An improved method for the preparation of DL-azetidine-2-carboxylic acid is reported. The reaction of thionyl chloride with azetidine-2-carboxylic acid in methanol gave rise to 2-carbomethoxyazetidine hydrochloride, which upon treatment with triethylamine yielded 2-carbomethoxyazetidine. 2-Carbomethoxyazetidine proved to be unstable and upon standing formed azetidine-2-carboxylic acid anhydride. The nmr and ir spectra of 2-carbomethoxyazetidine are discussed in terms of its conformation. The conversion of azetidine-2-carboxylic acid to azetidine-2-carboxamide is also described.

中文翻译：

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氮杂环丁烷-2-羧酸衍生物

报道了一种制备DL-氮杂环丁烷-2-羧酸的改进方法。亚硫酰氯与氮杂环丁烷-2-羧酸在甲醇中的反应产生了2-碳甲氧基氮杂环丁烷盐酸盐，将其用三乙胺处理后得到2-碳甲氧基氮杂环丁烷。证明2-碳甲氧基氮杂环丁烷是不稳定的，并且静置时形成氮杂环丁烷-2-羧酸酐。讨论了2-羰基甲氧基氮杂环丁烷的核磁共振和红外光谱。还描述了氮杂环丁烷-2-羧酸到氮杂环丁烷-2-甲酰胺的转化。