alkyl group having 3 to 7 carbon atoms in the definition of r 1 in the general formula i include a propyl butyl pentyl hexyl and heptyl group preferred is n pentyl group the streptovaricin c derivative of the general formula i has low toxicities against hiv noninfected mammalian cells and also in this point the anti aids virus agent of the present invention is excellent the streptovaricin c derivative of the general formula i has extremely low acute toxicities and for example in the case of the derivative having methyl group as the r 1 at c 19 position in the general formula i 50 lethal dose ld 50 against mouse is 1 000 mg kg or more in intramuscular administration and 3 000 mg kg or more in oral administration the streptovaricin c derivative of the general formula i as used in the present invention itself is known for example in u s pat no 4 212 881 and preparation isolation and purification thereof can be carried out according to the methods described in the patent according to the preparation method disclosed in the above u s pat no 4 212 881 the streptovaricin c derivative of the general formula i can be prepared by hydrolysis of streptovaricin c in a mild oxidizing condition to produce a streptovaricin c derivative corresponding the compound of the.