NEW MATERIAL:Fortimicin AL of formula I and its pharmacologically acceptable salt.

USE: An antibacterial and an intermediate for the synthesis of an antibiotic fortimicin AL derivative, e.g. the compound of formula II (R1 and R2 are H, acyl groups, etc.), effective against sensitive Gram-negative and Gram-positive bacteria, e.g. Escherichia coli, and useful as an intermediate for the synthesis of a derivative, e.g. 4-N-acyl- or N-alkylfortimicin AL.

PROCESS: A microorganism, e.g. Micromonospora olivoasterospora MK-70 strain (FERM-P No.1560), which belongs to the genus Micromonospora and has the ability to produce fortimicin AL, is incubated in a nutrient culture medium by the ordinary culture method for actinomyces to produce and accumulate the compound of formula I, which is then purified and isolated from the culture.