A new δ-valerolactone produced by marine Streptomyces sp. YIM 13591

A new δ-valerolactone compound, named 8-hydroxy invictolide 2 (1), a new natural product 4-hydroxy-3,5-dimethyl-6-(pentan-2-yl) tetrahydro-2H-pyran-2-one (2) together with four known compounds cyclo (L-Pro-L-Tyr) (3), cyclo (D-Pro-L-Tyr) (4), acetyltryptophan methyl ester (5), 2-aminobenzoic acid (6) were isolated from marine Streptomyces sp. YIM 13591. Their structures were elucidated by NMR spectroscopic data, HRESIMS and specific rotation, and the absolute configurations of the stereo centre in lactone ring 1 and 2 were further confirmed by electronic circular dichroism (ECD) calculation. The antimicrobial effects of these compounds were evaluated by the paper diffusion method.