The invention provides 5-deoxy-5,5-difluoro derivatives of aminoglycoside antibiotics of neamine, kanamycin A, kanamycin B, gentamicin and seldomycin, each synthesized as a novel compound, and also 1-N-(α-hydroxy-φ-aminoalkanoyl) derivatives synthesized from the newly obtained 5-deoxy-5,5-difluorokanamycins A and B and analogs thereof. The 5-deoxy-5,5-difluoro derivatives thus obtained have antibacterial activities superior or substantially equivalent to those of the amino-glycoside antibiotics from which they are derived and further have a remarkably improved median lethal dose (LD50) when intravenously administered to mice and a remarkably reduced toxicity on mammals.