Amikacin analogs with a fluorinated amino acid side chain

The synthesis and biological activity of kanamycin A derivatives with an omega-amino-alpha-fluoroalkanoyl side chain on the 1-amino group are described. The fluorinated amino acids (4) for the side chain were prepared by fluorination of the alpha-hydroxy esters (2) with diethylaminosulfur trifluoride (DAST) with accompanying the Walden inversion. The reaction products varied with the amino protective groups employed, chain length of the alkanoic acids and the presence or absence of base. The fluorinated side chain was introduced to 1-free-NH2 kanamycin A (12) by the conventional active ester method and subsequent deblocking reactions afforded the desired final products (13-17). Of the derivatives prepared, 1-N-[(S)-4-amino-2-fluorobutyryl]kanamycin A (2'''-deoxy-2'''-fluoroamikacin, 14) showed the best overall activity profile, nearly the same as that of amikacin. Preparation and antibacterial activity of several aminoglycoside antibiotics with the 1-N-(S)-4-amino-2-fluorobutyryl side chain are also discussed.