Cbz-L-Glu-(Cbz-L-Cys-OH)-Cbz-L-Cys-OH

Cbz-L-Glu-(Cbz-L-Ser-Bt)-Cbz-L-Ser-Bt

Cbz-L-Glu-(Cbz-L-Cys-Bt)-Cbz-L-Cys-Bt

Cbz-L-Glu-(Cbz-L-Ser-D-Pro-OH)-Cbz-L-Ser-D-Pro-OH

Cbz-L-Glu-(Cbz-L-Cys-D-Pro-OH)-Cbz-L-Cys-D-Pro-OH