Three 2"-modified dibekacin-analogs have been prepared as potential compounds active against resistant bacteria producing 2"-O-phosphotransferases; one is 5-deoxy-5,2"-diepi-5-fluorodibekacin (9) prepared from a suitably protected 2"-O-triflyl derivative through the 2" 3"-cyclic carbamate, and the others are 2"-oxo derivatives (12 and 22, both as the hydrate) of 5-deoxy-5-epi-5-fluoro-dibekacin and -arbekacin prepared through oxidation at C-2" of suitably protected derivatives. Relationships between the t-butoxycarbonyl(= Boc)-NH-shifts of per-N-Boc synthetic intermediates and their structures were studied. It was found that the shifts, measured in pyridine-d5 at 80 degrees C, which spread over a close range (delta 6-7 ppm), are sensitively influenced by nearby and surrounding groups around the BocNH group in respect of electron-withdrawing character, hydrogen bonding (BocNH ... acceptor), and also solvent effects (BocNH ... NC5H5).