Metals play essential roles in life
by coordination with small
molecules, proteins, and nucleic acids. Although the coordination
of copper ions in many proteins and methanobactins is known, the coordination
chemistry of Cu(II) in natural products and their biological functions
remain underexplored. Herein, we report the discovery of a Cu(II)-binding
natural product, chalkophomycin (CHM, 1), from Streptomyces sp. CB00271, featuring an asymmetric square-coordination
system of a bidentate diazeniumdiolate and a conjugated 1H-pyrrole 1-oxide-oxazoline. The structure of 1 may inspire
the synthesis of Cu(II) chelators against neurodegenerative diseases
or Cu(II)-based antitumor therapeutics.
A new benzophenone huanglongmycin (HLM) D (1) and two new monomeric xanthones huanglongmycin E (2) and F (3), together with four known aromatic polyketides aloesaponarin II (4) and the previously isolated huanglongmycin A-C (5-7) obtained from cave-derived Streptomyces sp. CB09001. The structures of 1-3 were established based on 1D, 2D NMR and HRMS data. Compounds 1-7 may be biosynthesized by a type II huanglongmycin polyketide synthase based on gene inactivation of hlmG encoding KSɑ in hlm gene cluster and their plausible biosynthetic mechanism was proposed.
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