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. Author manuscript; available in PMC: 2018 Feb 12.
Published in final edited form as: Biometals. 2015 Feb 8;28(3):541–551. doi: 10.1007/s10534-015-9830-3

Scheme 5.

Scheme 5

Synthesis of mixed-ligand siderophore-ciprofloxacin conjugate 23. Reagents and conditions: (i) 1. COCl2, toluene, rt; 2. N-1-Boc-1,4-butanediamine, Et3N, CH2Cl2, 0°C-rt, 91%; (ii) H2, Pd/C, MeOH, rt, 99%; (iii) 1. TFA, CH2Cl2, 0°C-rt; 2. Acid 19, EDC, HOBt, Et3N, DMAP, CH2Cl2, 0°C-rt, 50%; (iv) 1. TFA, CH2Cl2, 0°C-rt; 2. Acid 16, EDC, HOBt, Et3N, DMAP, CH2Cl2, 0°C-rt, 43%; (v) 1. LiOH, MeOH-H2O, 0°C-rt; 2. O-Allylciprofloxacin, EDC, HOBt, Et3N, DMAP, CH2Cl2, 0°C-rt, 55%; (vi) Pd(PPh3)4, sodium benzenesulfinate, AcOH, THF-MeOH, rt, 48%.