Absolute configuration of keisslone, a new antimicrobial metabolite from Keissleriella sp. YS4108, a marine filamentous fungus.

Abstract

In order to purify enough material for establishing the absolute stereochemistry of the new antifungal metabolite 3,6,8-trihydroxy-3-[3,5-dimethyl-2-oxo-3(E)-heptenyl]-2,3-dihydronaphthalen-1(4H)-one produced by Keissleriella sp., a marine filamentous fungus (strain number: YS 4108), a repeated growth and fractionation of the fungal culture was performed to give instead a new antimicrobial metabolite, keisslone (1), the structure of which was elucidated on the basis of spectral analyses including homo- and hetero-nuclear correlation NMR experiments (HMQC, COSY, NOESY and HMBC). The absolute configuration of metabolite 1 was determined mainly by its CD data and NOESY spectrum. The compound 1 was shown to be inhibitory against the human pathogenic fungi Candida albicans, Trichophyton rubrum and Aspergillus niger with MICs of 50, 70, 40 microg/mL, respectively. In order to purify enough material for establishing the absolute stereochemistry of the new antifungal metabolite 3,6,8-trihydroxy-3-[3,5-dimethyl-2-oxo-3(E)-heptenyl]-2,3-dihydronaphthalen-1(4 H)-one produced by Keissleriella sp., a marine filamentous fungus (strain number: YS 4108), a repeated growth and fractionation of the fungal culture was performed to give instead a new antimicrobial metabolite, keisslone (1), the structure of which was elucidated on the basis of spectral analyses including homo- and hetero-nuclear correlation NMR experiments (HMQC, COSY, NOESY and HMBC). The absolute configuration of metabolite 1 was determined mainly by its CD data and NOESY spectrum. The compound 1 was shown to be inhibitory against the human pathogenic fungi Candida albicans, Trichophyton rubrum and Aspergillus niger with MICs of 50, 70, 40 microg/mL, respectively.