The fermentation, isolation and structure elucidation of aklanonic acid are described. The compound was isolated from fermentations of Streptomyces strain ZIMET 43,717. Aklanonic acid is a yellow-orange crystalline substance, melting at 203-204'C (dec), having the molecular formula C:1H1sOs, and possessing UV maxima at 258, 282 (sh) and 438 nm (CHCI3). In dimethyl sulfoxide or pyridine aklanonic acid is unstable and a new compound (aklanone) is formed as a conversion product.The elucidation of the structures has shown that aklanonic acid and aklanone are derivatives of 1,8-dihydroxyanthraquinone.During our antibiotic screening program, a Streptomyces strain (designated as Streptomyces sp.ZIMET 43,717) was found to produce a new anthracycline-related pigment. The compound, which has been named aklanonic acid, is not active as an antibiotic. However, aklanonic acid is of particular interest because we have found that this compound was biotransformed to structurally different anthracyclinones in feeding experiments with several pigment-negative mutants"".Its role in the biosynthetic pathway of anthracyclines is now under study. The present paper is concerned with the physico-chemical properties of aklanonic acid and the results of the structural elucidation. The biological characteristics of the producing strain, which is unable to form aerial mycelia and spores, will be the subject of a separate communication.
Results
Isolation and Physico-chemical PropertiesAklanonic acid was obtained mainly from the mycelium by extraction with acetone. After purification by column chromatography and recrystallization from ethyl alcohol the compound was obtained as pure yellow-orange needles with a melting point of 203' 204°C (dec). Aklanonic acid is only slightly soluble in water, moderately soluble in ethyl alcohol, methanol, acetone and chloroform, and soluble in dimethyl sulfoxide and a solution of sodium bicarbonate in water. In concentrated sulfuric acid and sodium hydroxide the compound dissolves with a red color. When dissolved in dimethyl sulfoxide or pyridine aklanonic acid was rapidly converted to a new compound which we have named aklanone. The UV and visible spectrum of aklanonic acid in chloroform contains maxima at 258, 282 (sh), and 438 nm (s 23,300, 19,300, and 10,300). The IR spectrum in potassium bromide had characteristic absorptions at 1622, 1670 and 1700 cm-1.Aklanonic acid has the molecular formula C21H16O6. Attempts to derive the exact molecular formula based upon accurate molecular weight measurements by mass spectrometry and microanaly-