Strepyrrolins A–E, five pyrrole–sesquiterpene hybrids from Streptomyces sp. KIB 015, revealing a new formation logic of pyrroles by isotope labeling

Strepyrrolins A–E (1–5), five pyrrole–sesquiterpene hybrids were isolated from an endophytic Streptomyces . Isotope labeling experiments revealed that the pyrrole ring in strepyrrolins is constructed via a new logic in nature.