5-N-ACETYLARDEEMIN, A NOVEL HETEROCYCLIC COMPOUND WHICH REVERSES MULTIPLE-DRUG RESISTANCE IN TUMOR-CELLS .2. ISOLATION AND ELUCIDATION OF THE STRUCTURE OF 5-N-ACETYLARDEEMIN AND 2 CONGENERS

A family of novel compounds has been detected and isolated following an assay for the attenuation of multiple drug resistance in tumor cells from the fermentation broth and mycelia of a strain of Aspergillus fischeri which we have designated var. brasiliensis. The structures of three components were determined employing 1-D and 2-D homonuclear and heteronuclear NMR spectroscopy and mass spectrometry. The structure of 5-N-acetylardeemin was confirmed by single crystal X-ray diffraction. These compounds are most closely structurally related to asperlicin E1).