Secondary metabolites of Streptomyces sp. A1693

: By means of various chromatographic methods such as Sephadex LH-20，ODS，and semi-preparative HPLC，ten compounds were isolated from Streptomyces sp. A1693 and their structures were elucidated on the basis of spectroscopic data and physico-chemical methods. The compounds comprised 5 butenolides，2 diketopiperazines，and 3 antimycin antibiotics. The structures were identified as (5S)-5-(11-hydroxymethyloctyl)furan-2(5H)-one (1), (5S)-5-(11-hydroxy-11-methylheptyl)furan-2(5H)-one (2), (5S)-5-(11-methyl-12-oxooctyl) furan-2(5H)-one (3), (5S)-5-(11-hydroxy-11-methyloctyl)furan-2(5H)-one (4), (5S)-5-(11-hydroxy-12-methyloctyl)furan-2(5H)-one（5），cyclo-Phe-Val (6)，cyclo-Phe-Ile (7)，uranchimycin A (8)，uranchimycin B (9)，and deisovalerylblastomycin (10). Among them，1 was defined as a new compound. All the compounds didn't show the cytotoxic activity against A549 cell line (IC₅₀>50 mg·L⁻¹).