Bruker400 ultrashield nmr spectrometer

Analysis was performed using a Bruker
400 ultrashield NMR spectrometer. ¹H and ¹³C
NMR results were collected at a frequency
of either 400 or 101 MHz, respectively. For ¹H NMR, a spectral
window of 20 ppm, a relaxation delay of 1 s, and 128 scans with automatic
lock and shimming at a concentration of 15 mg/mL have been applied.
For ¹³C NMR, a spectral window of 240 ppm, a relaxation
delay of 2 s, and 512 scans with automatic lock and shimming at a
concentration of 150 mg/mL have been applied. The obtained spectra
were analyzed using Mest ReNova version 9.0.0-12821.

All reagents and solvents were purchased from commercial vendors and used without purification. 4-Amino-2-methoxybenzoic acid (97%), N,N-diisopropylethylamine (DIPEA, >98%), N,N-diethylethylenediamine (DEDA, >98%), ammonium hydroxide (NH₄OH), iodine monochloride, and trifluoroacetic acid (TFA, 99%) were purchased from ACROS Organics (Morris, NJ, USA). 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) was obtained from Biosynth Carbosynth (Berkshire, UK). 1-Hydroxybenzotriazole hydrate (HOBt) and 5-fluoropyridine-2-carboxylic acid (98%) were purchased from AK Scientific, Inc. (Union City, CA, USA). 6-Fluoronicotinic acid (98%) was purchased from Accela ChemBio Co., Ltd. (Shanghai, China). Magnesium sulfate (MgSO₄), potassium carbonate (K₂CO₃), and thionyl chloride (SOCl₂) were obtained from Merck KGaA (Darmstadt, Germany). Thin-layer chromatography (TLC) was performed by silica gel F254-coated aluminum-backed plates (Merck KGaA, Darmstadt, Germany). Nuclear magnetic resonance (NMR) spectra were determined by the Bruker 400 UltraShield NMR spectrometer (Bruker, Billerica, MA, USA) at the Instrumentation Resource Center of National Yang-Ming University (Taipei, Taiwan). The radioactivity was measured by the γ-counter (PerkinElmer 1470 Automatic Gamma Scintillation, PerkinElmer Inc., Shelton, CT, USA).