Facile synthesis of structurally diverse 5-oxopiperazine-2-carboxylates as dipeptide mimics and templates
作者:Michael Limbach、Alexander V. Lygin、Vadim S. Korotkov、Mazen Es-Sayed、Armin de Meijere
DOI:10.1039/b908548c
日期:——
A sequence of Michael addition of a primary amine onto methyl 2-chloro-2-cyclopropylidene-acetate (1), acylation of the adduct with α-bromo acid chlorides under modified Schotten-Baumann conditions and ring-closing twofold nucleophilic substitution on the thus formed bishalides 3a–e with aliphatic or aromatic amines according to a very simple protocol with final acid/base extraction or filtration over silica gel for purification leads to the 3-spirocyclopropanated 5-oxopiperazine-2-carboxylates 2 or in two cases, after intermolecular transesterification of 2, to bicyclic oxopiperazines 6, with a remarkable variability of the substituents R1–R3 in 39–99% yields (20 examples). Starting with α-bromophenylacetic acid chloride, the trans-configured 6-phenyl-5-oxopiperazine-2-carboxylates are formed preferentially.
一系列的迈克尔加成反应,将伯胺加成到甲基2-氯-2-环丙叉基乙酸酯(1)上,然后在改进的Schotten-Baumann条件下用α-溴代酸酰氯进行酰化反应,接着通过非常简单的方案,用脂肪族或芳香族胺对生成的双卤化物3a–e进行环闭二重亲核取代反应,最后通过酸/碱萃取或硅胶过滤进行纯化,得到3-螺环丙烷化的5-氧代哌嗪-2-羧酸酯2,或者在两个情况下,经过分子间酯交换反应,得到双环氧哌嗪6,这些化合物具有显著的取代基R1–R3的多样性,产率在39–99%(20个例子)。从α-溴苯乙酸氯开始,优先形成反式构型的6-苯基-5-氧代哌嗪-2-羧酸酯。