Structure of the pentaene antibiotic roseofungin

: Roseofungin is a pentaene antibiotic of the subgroup of carbonyl conjugated pentaenes. Oxidation of the antibiotic perhydroderivative in succession with potassium permanganate and chromic anhydride resulted in formation of 2-methyltridecan dicarboxylic acid evident of the methyl branching in the roseofungin chromophore. To justify the position of the oxygen-containing functions, the polyoles resulting from reduction of the antibiotic and the products of its isonolysis were investigated by mass-spectrometry. The use of lithium alumina boron deiteride and sodium boron deiteride as reducers provided determination of two carbonyls (C11 and C17) in the roseofungin molecule. 13C NMR spectroscopy revealed the presence of the hemiketal ring formed at the expense of carbonyl C17 and carbonyl C21.