COMPLETE H-1 AND C-13 NMR ASSIGNMENTS FOR APRAMYCIN, SISOMICIN AND SOME N-POLYACETYLATED AND N,O-POLYACETYLATED AMINOGLYCOSIDES

The H-1 NMR spectra (300 MHz) of the aminoglycoside antibiotics apramycin and sisomicin (free bases) were completely analysed by 1D and 2D methods (mainly H-1-H-1 and H-1-C-13 shift-correlation spectroscopy). The complete H-1 nd C-13 NMR assignment of a series of semisynthetic N-polyacetyl- and N,O-polyacetyl derivatives of kanamycins A and B, tobramycin, apramycin and sisomicin was also achieved via these techniques. The effect of acetylation on the H-1 and C-13 chemical shifts, H-1-H-1 coupling constants and ring conformations is discussed. The vicinal coupling constants for the unsaturated ring in sisomicin, calculated on the basis of the energetically favoured conformation predicated by the MMP2 method, are in good agreement with the experimental data.