Chemical modification of some gentamicins and sisomicin at the 3''-position.

Chemical and photochemical oxidative methods of de-N-methylation of some gentamicins and sisomicins at the 3''-position are described. Selective acetylation of gentamicins and sisomicins at the 1, 3, 2' and 6' and of gentamicin B at the 1, 3, and 6'positions are achieved by treatment of the free bases with carbon dioxide prior to acetylation. De-N-methylation of the above selectively blocked gentamicins and sisomicins followed by re-alkylation at the 3''-position and de-N-protection gives a series of 3''-N-alkyl analogues. The in vitro antibacterial properties of the new derivatives of gentamicins and sisomicins are given.