Polyketides and Anthranilic Acid Possessing 6-Deoxy-α-l-talopyranose from a Streptomyces Species

A bioassay-guided investigation in conjunction with chemical screening led to the isolation of three new glycosides, ulleungoside (1), 2-methylaminobenzoyl 6-deoxy-α-l-talopyranoside (2), and naphthomycinoside (3), along with three known secondary metabolites (5-7) from Streptomyces sp. KCB13F030. Their structures were elucidated by detailed NMR and MS spectroscopic analyses. Absolute configurational analysis of the sugar units based on the magnitudes of the coupling constants, NOESY correlations, chemical derivatization, and optical rotation measurements revealed that compounds 1-3 and 5 incorporate the rare deoxyhexose 6-deoxy-α-l-talopyranose. The absolute configuration of a polyketide extender unit of 3 was determined by applying the J-based configuration analysis and modified Mosher's method. Ulleungoside (1) and naphthomycin A (7) showed in vitro inhibitory effects against indoleamine 2,3-dioxygenase activity. Further bioevaluation revealed that compounds 1 and 7 had moderate antiproliferative activities against several cancer cell lines, and compounds 5 and 6, which are members of the piericidin family, induced autophagosome accumulation.