(±)-Pyriindolin with a 2,2′-bipyridine-spiro[furan-3,3′-indoline] chimeric skeleton from the endophytic Streptomyces albolongus EA12432

Abstract (±)-Pyriindolin (1) with a rare molecular backbone formed by fusing a 2,2′-bipyridine nucleus into a spiro[furan-3,3′-indoline] skeleton, was isolated from the Streptomyces albolongus EA12432. The constitution and the relative configuration of (±)-1 were determined by extensive spectroscopic analyses, 13C calculation and DP4+ probability analysis. The absolute configurations of optically pure (+)-1 and (−)-1 which were obtained after a chiral high performance liquid chromatography (HPLC) separation were further identified by electronic circular dichroism (ECD) calculations. (+)- and (−)-Pyriindolins displayed moderate cytotoxicity against HCT-116 cell line with the half-maximal inhibitory concentration (IC50) values of 2.89 ± 0.17 μmol/L and 4.47 ± 0.26 μmol/L, respectively.