Experimental data on the chemical transformations of the antibiotic fervenulin and its analogs have been analyzed and compared to the results of recent physicochemical investigations. Crystals of donor -acceptor complexes of fervenulin and its 4-N-oxide with indoles have been obtained, their IR spectra have been studied, and their x-ray structure analysis was performed for the first time. Information concerning the reaction sites of the fervenulin molecule is obtained.