Four pentapeptide N-hydroxysuccinimide esters [X–Orn(Z)–Leu–Y–Pro–ONSu (X=Val or d-Val, and Y=Phe or d-Phe)] related to gramicidin S were allowed to cyclize in pyridine. The peptides with a l-Phe residue preceding Pro tend to form various cyclic polymers, while ones with a d-Phe residue exclusively yielded a cyclic monomer or cyclic dimer. Peptides with a d-Val residue at the N-terminal produced monomerization products. The observed tendencies were similar for cyclization of four hexapeptide N-hydroxysuccinimide esters [X–Val–Orn(Z)–Leu–Y–Pro–ONSu (X=Tyr(Bzl) or d-Tyr(BzlCl2), and Y= Phe or d-Phe)] related to gratisin.
                                    与gramicidin S相关的四个五肽N-羟基琥珀
酰亚胺酯[X–Orn(Z)–Leu–Y–Pro–ONSu (X=Val或d-Val,Y=Phe或d-Phe)]在
吡啶中环化。在Pro之前带有l-Phe残基的肽倾向于形成各种环状聚合物,而带有d-Phe残基的肽仅产生环状单体或环状二聚体。在N端带有d-Val残基的肽产生单体化产物。与gramicidin S相关的四个六肽N-羟基琥珀
酰亚胺酯[X–Val–Orn(Z)–Leu–Y–Pro–ONSu (X=Tyr(Bzl)或d-Tyr(BzlCl2),Y= Phe或d-Phe)]的环化趋势与上述相似。