Benoiton N L, Lee Y C, Chen F M
Department of Biochemistry, University of Ottawa, Ontario, Canada.
Int J Pept Protein Res. 1993 Apr;41(4):338-41. doi: 10.1111/j.1399-3011.1993.tb00449.x.
Mixed anhydrides from Z-valine and ethyl, isobutyl, isopropyl and isopropenyl chloroformate, and from N-tert-butoxycarbonyl- (Boc) and N-benzyloxycarbonyl- (Z) leucine and phenylalanine and Boc- and N-9-fluorenylmethoxycarbonyl-valine and ethyl chloroformate were purified and left in dichloromethane at 23 degrees C. The symmetrical anhydride (SyAn) generated after 24 h was determined by normal phase high-performance chromatography. No SyAn was produced from the anhydrides of Z- and Boc-valine; SyAn was produced from the other anhydrides. Anhydrides examined without isolation generally produced more SyAn than the pure compounds. More SyAn was generated in dimethylformamide and tetrahydrofuran than in dichloromethane, or in the presence of an excess of N-methylmorpholine or triethylamine. The anhydride from isobutyl chloroformate was much more stable than the anhydride from ethyl chloroformate. It is suggested that disproportionation of pure mixed carboxylic acid--carbonic acid anhydrides occurs by a bimolecular mechanism.
对Z-缬氨酸与氯甲酸乙酯、异丁酯、异丙酯和异丙烯酯形成的混合酸酐，以及N-叔丁氧羰基-（Boc）和N-苄氧羰基-（Z）亮氨酸、苯丙氨酸与Boc-和N-9-芴甲氧羰基-缬氨酸和氯甲酸乙酯形成的混合酸酐进行纯化，并在23℃下置于二氯甲烷中。24小时后生成的对称酸酐（SyAn）通过正相高效色谱法测定。Z-和Boc-缬氨酸的酸酐未生成SyAn；其他酸酐生成了SyAn。未经分离检测的酸酐通常比纯化合物生成更多的SyAn。在二甲基甲酰胺和四氢呋喃中生成的SyAn比在二氯甲烷中多，或在存在过量N-甲基吗啉或三乙胺的情况下生成的SyAn更多。氯甲酸异丁酯形成的酸酐比氯甲酸乙酯形成的酸酐稳定得多。有人提出，纯混合羧酸-碳酸酐的歧化反应是通过双分子机制发生的。
