Discovery of a new asymmetric dimer nenestatin B and implications of a dimerizing enzyme in a deep sea actinomycete.

Benzofluorene-containing atypical angucyclines are an important family of natural products with a broad spectrum of antibacterial and cytotoxic properties. Interestingly, symmetric and asymmetric dimers showed better activity than the monomer in this class of compounds. Herein, we reported the isolation of a new asymmetric dimer nenestatin B (2) from the deep sea actinomycete Micromonospora echinospora SCSIO 04089 and a monomer nenestatin C (3) from an NmrA family regulatory protein coding gene nes18 inactivated mutant. The structural elucidation of 3 indicated the essential role of Nes18 in the biosynthetic pathway of 2, specifically in dimerization via C-C bond formation.