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

摘要

Previously chemical investigation of the marine-derived Streptomyces pratensis strain KCB-132, cultivated in liquid ISP2 medium, had led to the discovery of three C-ring cleavage angucyclinone N-heterocycles, pratensilins A–C, with a spiro indolinone-naphthofuran skeleton. Addition of 50 μM LaCl3 to the same medium and subsequently chemical analysis of this strain returned a new member of this rare class, pratensilin D (1), along with two new angucyclinone derivatives, featuring ether-bridged (2) and A-ring cleavage (3) structural properties, respectively. Their structures and absolute configurations were assigned by spectroscopic analysis, single-crystal X-ray diffractions and ECD calculation. (+)- and (?)-1, a pair of enantiomers, exhibited different strengths of antibacterial and cytotoxic activities.