AUTHOR=Guo Lin , Zhang Lu , Yang Qiaoli , Xu Bo , Fu Xinzhen , Liu Ming , Li Zhi , Zhang Shumin , Xie Zeping 

TITLE=Antibacterial and Cytotoxic Bridged and Ring Cleavage Angucyclinones From a Marine Streptomyces sp

JOURNAL=Frontiers in Chemistry

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.00586

DOI=10.3389/fchem.2020.00586

ISSN=2296-2646

ABSTRACT=<p>Chemical investigation of a marine-derived <italic>Streptomyces</italic> sp. KCB-132, cultivated in liquid ISP2 medium, had led to the discovery of three C-ring cleavage angucyclinone <italic>N</italic>-heterocycles, pratensilins A–C, with a novel spiro indolinone-naphthofuran skeleton. Addition of 50 μM LaCl<sub>3</sub> to the same medium and subsequent chemical analysis of this strain returned a new member of this rare class, pratensilin D (<bold>1</bold>), along with two new angucyclinone derivatives, featuring ether-bridged (<bold>2</bold>) and A-ring cleavage (<bold>3</bold>) structural properties. Their structures and absolute configurations were assigned by spectroscopic analysis, single-crystal X-ray diffractions, and equivalent circulating density (ECD) calculations. (+)- and (–)-<bold>1</bold>, a pair of enantiomeric nitrogen-containing angucyclinones, exhibited different strengths of antibacterial and cytotoxic activities.</p>