This review describes a selection of macrocyclic natural products and structurally
modified analogs containing peptidic and non-peptidic elements as structural features
that potentially modulate cellular permeability. Examples range from exclusively peptidic
structures like cyclosporin A or phepropeptins to compounds with mostly non-peptidic
character, such as telomestatin or largazole. Furthermore, semisynthetic approaches
and synthesis platforms to generate general and focused libraries of compounds at
the interface of cyclic peptides and non-peptidic macrocycles are discussed.
