Study on fluorination-toxicity relationships. Syntheses of 1-N-[(2R,3R)- and (2R,3S)-4-amino-3-fluoro-2-hydroxybutanoyl] derivatives of kanamycins.

(2R,3R)- And (2R,3S)-4-azido-3-fluoro-2-hydroxybutanoic acids (11 and 22) have been prepared from 3-deoxy-3-fluoro-1,2-O-isopropylidene-alpha-D-glucofuranose (1) and 3,5-di-O-benzyl-1,2-O-isopropylidene-alpha-D-xylofuranose (12), respectively. They were then coupled to the N2N-1 group of suitably protected kanamycin A or kanamycin B analogs to give, 1-N-[(2R,3R)- and (2R,3S)-4-amino-3-fluoro-2-hydroxybutanoyl]kanamycins (32-35). This group of compounds (32-34) exhibited similar antibacterial activity and toxicity level as those of the corresponding 1-N-[(S)-4-amino-2-hydroxybutanoyl] (AHB) derivatives of kanamycins. The base strength of the H2N-4"' group of 32 and 34, as determined by 13C NMR spectroscopy (in D2O) at varying pD values, was found to be lower when compared to the basicity for the corresponding AHB analogs. The relationship between observed toxicity and base strength of the H2N-4"' group is discussed.