Figure 1.

Structures of representative aminoglycoside antibiotics. Kanamycin A and gentamicin C1a are 4,6-disubstituted aminoglycosides, neomycin B is a 4,5-disubstituted aminoglycoside, and streptomycin is an atypical aminoglycoside. The rings are labeled B (the central deoxystreptamine ring in the first three molecules, and the ribose moiety in streptomycin), and A, C, and D if necessary, for the substituted glycan rings. The functional groups available for modification by various aminoglycoside-modifying enzymes are numbered.