Reaction ofγ-Hydroxy-N-[1-(dimethylcarbamoyl)ethyl]butanamides under the ‘Direct Amide Cyclization’ Conditions
作者:Boyan Iliev、Anthony Linden、Heinz Heimgartner
DOI:10.1002/hlca.200690008
日期:2006.1
the imino lactones was achieved by increasing the substitution in the five-membered ring, and their structure, in the form of the hydrochlorides, was established independently by X-ray crystallography (Fig. 4). A derivative 15 of the imino lactone 12a was prepared by the reaction with the 2H-azirin-3-amine 10a; its structure was also established by an X-ray crystal-structure determination (Fig. 3).
标题化合物的制备是通过“叠氮基/恶唑酮法”从相应的γ-羟基酸开始的。将γ-羟基-N- [1-(二甲基氨基甲酰基)乙基]丁酰胺4置于所谓的“直接酰胺环化”(DAC)条件下,即可得到氯化酸11或亚氨基内酯12作为唯一的产物。预期的环二肽A或它们的环二聚体(方案4)。4中取代基的变化不影响反应的结果,并且已经提出了由中间体恶唑酮13形成两种产物的机理。在DAC的酸性条件下,亚氨基内酯以其HCl盐12的形式形成,其在极性溶剂中或在硅胶上进一步反应生成氯化酸11。亚氨基内酯的稳定化是通过增加五元环中的取代来实现的,它们的盐酸盐形式的结构通过X射线晶体学独立建立(图4)。亚氨基内酯12a的衍生物15通过与2 H-叠氮基-3-胺反应而制备。10a ; 通过X射线晶体结构确定也确定了其结构(图3)。此外,通过X射线晶体学确定ω-氯酸11a和11b的结构(图2)。