2′-N-acylfortimicins and 2′-N-alkylfortimicins via the isofortimicin rearrangement1

Abstract Fortimicin A and a number of 4- N -acylfortimicins B, although stable as either the fully protonated hydrochloride or sulfate salts, undergo degradation as the free bases in aqueous solution. Detailed studies with fortimicin A and 4- N -acetylfortimicin B have shown that degradation occurs, in part, by simple cleavage of the 4- N -acyl groups with formation of fortimicin B, and, in part, by rearrangement to the 2′- N -acylfortimicins B (the isofortimicin rearrangement). The conversions of the rearrangement products into 2′- N -glycylfortimicin A, 2′- N -acetylfortimicin A, and the 2′- N -(2-aminoethyl)fortimicins A and B are described. The antibacterial activities of the new fortimicin A derivatives are presented.