The inventors have discovered, during the course of their histological studies on antitumor agents, the novel antitumor antibiotic BMG 162-aF2, later named spergualin, in a broth for culture of Bacillus laterosporus BMG 162-aF2 (Deposit No. 5230 at the Fermentation Research Institute, Agency of Industrial Science and Technology, Ministry of International Trade and Industry of Japan), a strain belonging to the genus Bacillus (Journal of Antibiotics, Vol. 34, 1619-1622, 1981), The chemical structure of spergualin is represented by the following formula ##STR3## in which the configuration at the 15-position is S-configuration (sinister), but that at the 11-position has not been determined (Journal of Antibiotics, vol. 34, 1622, 1981).
The compound of this structural formula could also be synthesized by the condensation of an acid amide and glyoxylylspermidine, and the resulting epimer was divided into (-)-spergualin that naturally occurs and (+)-spergualin that does not (Journal of Antibiotics, Vol. 34, 1625, 1981).