ABSTRACT
The concept that flat ring-shaped cyclopeptides have the potential to aggregate as “endless” stacks through backbone-backbone hydrogen bond interactions dates back to 1974 (Fig. 2.2) [49]. As early as the following year, the crystal structure of cyclo-Ser(OtBu)-β-Ala-Gly-β-Asp(OMe) was published (Fig. 2.3) [50]. Although its structure consisted in the parallel packing of tubular stacks, only half of the amides capabilities for hydrogen bonding were fulfilled.
