Ulleungdolin, a Polyketide–Peptide Hybrid Bearing a 2,4-Di-O-methyl-β-d-antiarose from Streptomyces sp. 13F051 Co-cultured with Leohumicola minima 15S071

A new secondary metabolite, ulleungdolin (1), was isolated from the co-culture of an actinomycete, Streptomyces sp. 13F051, and a fungus, Leohumicola minima 15S071. Based on the NMR, UV, and MS data, it was deduced that the planar structure of 1 comprised an isoindolinone (IsoID) with an octanoic acid, a tripeptide, and a sugar. The tripeptide has the unprecedented amino acids norcoronamic acid, 3-hydroxy-glutamine, and 4-hydroxy-phenylglycine and is linked by a C-N bond with IsoID. The absolute configurations were determined by chemical derivatization, extensive spectroscopic methods, and electronic circular dichroism calculations and supported by bioinformatic analyses. Bioactivity evaluation studies indicated that 1 had an antimigration effect on MDA-MB-231 breast cancer cells.