Ball milling was exploited to prepare a substituted proline building block by mechanochemical nucleophilic substitution. Subsequently, the mechanocoupling of hindered proline amino acid derivatives was developed to provide proline–proline dipeptides under solvent-free conditions. A deprotection–cyclization sequence yielded the corresponding diketopiperazines that were obtained with a high stereoselectivity which could be explained by DFT calculations. Using this method, an enantiopure disubstituted Pro–Pro diketopiperazine was synthesized in 4 steps, making 5 new bonds using a ball mill.
球磨法被利用来通过机械化学亲核取代制备一个取代的脯氨酸构建块。随后,发展了受阻脯氨酸衍生物的机械偶联,以在无溶剂条件下提供脯氨酸-脯氨酸二肽。去保护-环化序列产生了相应的二酮哌嗪,其高立体选择性可以通过DFT计算来解释。使用这种方法,一个对映纯的二取代脯氨酸-脯氨酸二酮哌嗪在4个步骤中合成,利用了球磨机制造了5个新键。