N n diisopropylethyl amine dipea trifluoroacetic acid tfa

All Fmoc amino acids, reagents, and solvents were used without purification. Fmoc amino acids and 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo [4,5-b]pyridinium 3-oxid hexafluorophosphate (HATU) were purchase from AAPPTec, Bachem, Chem-Impex, ChemPep, and PurePep. The Rink amide ChemMatrix resin (catalog number: 7-600-1310) was purchased from Biotage. The 2-chlorotrityl chloride (2-CTC) resin (catalog number: 150301) were purchased from ChemPep. N,N-dimethylformamide (DMF), CH₂Cl₂, MeCN, MeOH, Et₂O, AcOH, Ac₂O, N,N-diisopropylethylamine (DIPEA), trifluoroacetic acid (TFA), NH₄HCl, NH₄HCO₃, urea, NaOH, 80% hydrazine hydrate, 2-mercaptoethanol were purchased from Fisher Scientific. Piperidine, triisopropylsilane (TIPS), hydroxybenzotriazole (HOBt), N,N′-diisopropylcarbodiimide (DIC), 2,2′-dithiodipyridine (DTDP), 2,2′-dithiobis (5-nitropyridine) (DTNP), I₂, Pd(PPh₃)₄, 1,3-dimethylbarbituric acid (DMBA), glucose, sodium ascorbate were purchased from Sigma Aldrich. 4-carboxy-3-fluorophenylboronic acid was purchased from Alfa Aesar. Agilent 6120 Quadrupole LC‒MS system was used to acquire the LC chromatograms and mass spectra of samples with Luna^® 5 μm C18 100 Å (50 × 2 mm) column (Phenomenex, CA, United States) at 0.4 ml/min with 5% of a H₂O/MeCN + 0.1% TFA solution for 1 min followed by a linear gradient from 5% to 95% of a H₂O/MeCN + 0.1% TFA solution over 5 min.