Four previously undescribed angucyclinones umezawaones A-D (1-4) were isolated from the liquid cultures of Umezawaea beigongshangensis. Their structures were determined by spectroscopic analyses, single crystal X-ray diffraction, quantum chemical 13C NMR and electronic circular dichroism calculations. All compounds displayed strong inhibitory activities against indoleamine 2,3-dioxygenase and tryptophan-2,3-dioxygenase in enzymatic assay, especially compound 2.
Actinobacteria , Tryptophan Oxygenase , Tryptophan Oxygenase/chemistry , Tryptophan Oxygenase/metabolism , Angucyclines and Angucyclinones , Actinomyces/metabolism , Indoleamine-Pyrrole 2,3,-Dioxygenase , Molecular Structure
A sustainable pathway for the synthesis of tetracyclic purinium salts via ruthenium-catalyzed electro-oxidative annulation of C6-arylpurine nucleosides with alkynes without a stoichiometric metal oxidant has been developed. The protocol described herein exhibits high regioselectivity, broad scope, and wide functional group tolerance, allowing efficient coupling of various biologically important molecules including acyclic, ribosyl, arabinosyl, and deoxyribosyl purine nucleoside derivatives. A novel purinoisoquinolinium-coordinated ruthenium(0) sandwich intermediate has been isolated, crystallographically characterized, and electrochemically analyzed, offering direct mechanistic insight.
