(2R,3R)-trans-Epoxysuccinyl-dipeptides (7a-7d) were synthesized by acylation of dipeptides with the N-hydroxysuccinimide or pentafluorophenyl ester of monoethyl (2R,3R)-trans-epoxysuccinate (6a,6b). A nucleophilic oxirane ring opening by N-hydroxysuccinimide and pentafluorophenol during the preparation of the active esters could not be observed. Subsequent saponification of the monoethyl ester 7a-7d with KOH in ethanolic solution allowed to produce the dipeptide derivatives as potassium salts (8a,8d) which were found to be stable on storage in the cold. The attempts to convert (2R,3R)-trans-epoxysuccinyl-glycyl-proline (7a) into the corresponding (2S,3S)-trans-epithiosuccinyl derivative via an oxygen sulfur exchange reaction with 3-methylbenzothiazole-2-thione failed completely as among the various products of unknown nature formed only the desulfurated fumaryl derivative could be isolated and characterized.
(2R,3R)-反式-环氧丁二酰二肽(7a-7d)是通过使用单乙基(2R,3R)-反式-环氧
丁二酸酯(6a,6b)的N-羟基丁二
酰亚胺或
五氟苯酯对二肽进行酰化反应合成的。在制备活性酯的过程中,无法观察到由N-羟基丁二
酰亚胺和
五氟苯酚引发的
环氧乙烷环的亲核开环反应。随后,将单
乙酯7a-7d与
乙醇溶液中的
氢氧化钾进行皂化反应,生成了作为
钾盐的二肽衍
生物(8a,8d),这些衍
生物在冷处保存时表现出稳定性。尝试通过与3-甲基
苯并噻唑-2-
硫酮进行氧
硫交换反应将(2R,3R)-反式-环氧丁二酰甘
氨酰脯
氨酸(7a)转化为相应的(2S,3S)-反式-环氧丁二
硫酰衍
生物,但这一尝试完全失败。在生成的各种未知性质产物中,唯一能分离并表征的是脱
硫的富马酰衍
生物。