Table 1. Comparison of the Determined pKa Values of Individual Amino Groups Among Apramycin, Tobramycin, Gentamicin, Amikacin, Arbekacin, and Plazomicina.
| aminoglycoside | method | N-1 | N-3 | N-2′ | N-6′ | N-7′ | N-4′′ | N-3′′ | N-4′′′ |
|---|---|---|---|---|---|---|---|---|---|
| apramycin | 15N–1H HMBC NMR | 8.5 ± 0.3 | 7.0 ± 0.2 | nd | 7.52 ± 0.10 | 7.1 ± 0.3 | |||
| 1H NMR | 8.3 ± 0.2 | 7.17 ± 0.06 | 7.96 ± 0.09 | 7.51 ± 0.08 | 6.92 ± 0.08 | ||||
| tobramycin | 15N–1H HMBC NMR | 7.81 ± 0.06 | 6.93 ± 0.03 | nd | 8.90 ± 0.06 | 7.82 ± 0.08 | |||
| 1H NMR | 7.61 ± 0.09 | 7.03 ± 0.12 | 8.07 ± 0.09 | 9.0 ± 0.3 | 7.75 ± 0.07 | ||||
| gentamicin | 15N–1H HMBC NMR | 7.84 ± 0.10 | 7.15 ± 0.10 | nd | 9.2 ± 0.2 | 8.54 ± 0.07 | |||
| 1H NMR | nd | nd | nd | 9.73 ± 0.16 | 8.53 ± 0.15 | ||||
| amikacin | 15N–1H HMBC NMR | 7.53 ± 0.13 | 8.76 ± 0.13 | 7.96 ± 0.11 | 9.6 ± 0.4 | ||||
| 1H NMR | 7.35 ± 0.14 | 8.7 ± 0.2 | 7.81 ± 0.16 | 9.8 ± 0.3 | |||||
| arbekacin | 15N–1H HMBC NMR | 7.39 ± 0.10 | nd | nd | 7.94 ± 0.07 | 9.71 ± 0.08 | |||
| 1H NMR | 7.26 ± 0.18 | 8.47 ± 0.19 | 9.11 ± 0.04 | 7.7 ± 0.2 | 9.8 ± 0.2 | ||||
| plazomicin | 15N–1H HMBC NMR | 7.84 ± 0.11 | 8.06 ± 0.08 | 8.52 ± 0.11 | 8.57 ± 0.08 | 9.74 ± 0.10 | |||
| 1H NMR | 7.8 ± 0.4 | 7.83 ± 0.14 | 8.43 ± 0.07 | 8.65 ± 0.05 | nd |
a
nd-not determined.