Two new butenolides produced by an Actinomycete Streptomyces sp.

Two new butenolides, (4S)-4,10-dihydroxydodec-2-en-1,4-olide (1) and (4S)-4,8,10-trihydroxy-10-methyldodec-2-en-1,4-olide (2), together with three known compounds, MKN-003B (3), MKN-003C (4), and cyclo(Ala-Leu) (5), were isolated from the culture broth of a bacterium of the genus Streptomyces derived from soil environment. The structures of these compounds were elucidated on the basis of spectroscopic analysis. The inhibitory activities of the butenolides against eight pathogenic fungi were evaluated. All of the butenolides showed moderate-or-weak antifungal activities in a broth microdilution assay.