We report herein new labile protecting groups of N-carboxyanhydrides (NCA) useful to prevent polymerization during coupling reactions with nitrogen nucleophiles. Thus, N-sulfinyl-NCA 1 and N-silyl-NCA 2 were prepared in situ and involved, without being isolated, in coupling reactions with various α-amino esters to furnish dipeptides 3 and unsymmetrical peptidyl ureas 4, respectively, in good yields.
我们在此报道了新的N-羧基环内酐(NCA)不稳定保护基团,这些基团在氮亲核试剂参与的偶联反应中能有效防止聚合反应的发生。因此,N-亚砜基NCA 1和N-
硅基NCA 2在反应中现场制备,并未分离出来,而是直接与各种α-
氨基酯进行偶联反应,分别以良好收率得到了二肽3和不对称肽
脲4。