Piperidine

The
deuterated solvent (CDCl₃)
used for NMR spectroscopy, silica gel 60 (230–400 mesh) for
column chromatography, trifluoroacetic acid, p-chloranil,
MB, DPBF, triethylamine, benzene, acetonitrile, sodium ascorbate,
copper sulfate pentahydrate, cresyl violet, and boron trifluoride
diethyl etherate were provided by Merck. The following chemicals were
obtained from Sigma-Aldrich: ethanol, methanol tetrahydrofuran, sodium
thiosulfate, dimethyl sulfoxide, 2,4-dimethylpyrrole, N,N-dimethylformamide, acetone, dichloromethane,
iodic acid, iodine, hexane, sodium sulfate, N-bromosuccinimide, and glacial acetic acid. n-Butylamine was purchased from Alfa Aesar. The following
chemicals were obtained from Acros Organics: piperidine and 4-hydroxybenzaldehyde.
Bromo-1,8-naphthalic anhydride was purchased from TCI. Zinc phthalocyanine
and 1-azido-1-deoxy-β-d-glucopyranoside tetraacetate
were purchased from ABCR. The rest of the chemicals used in the synthesis
were of reagent grade unless otherwise specified.

All solvents and reagents were purchased from commercial sources and used without further purification. All amino acid derivatives, 2-chlorotrityl chloride (2 Cl Trt) resin and 2-(7-Aza-1H-benzotriazole-1-yl)–1,1,3,3-tetramethyluronium hexafluorophosphate (HATU) were purchased from Novabiochem, Merck (Darmstadt, Germany). N,N-Dimethylformamide (DMF), N,N-diisopropylethylamine (DIEA), and piperidine were from Acros Organics (Geel, Belgium). O-(6-Chlorobenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HCTU) was from Carl Roth GmbH (Karsruhe, Netherlands). Hydrazine monohydrate was purchased from Alfa Aesar (Heysham, UK), acetonitrile (ACN) from Avantor Performance Materials (USA). Tentagel S RAM resin, hydroxybenzotriazole (HOBt), tris(2-carboxyethyl)phosphine (TCEP), diethylether, phenylsilane, tetrakis(triphenylphosphine)palladium(0), trifluoroacetic acid (TFA), dichloromethane (DCM), triisopropylsilane (TIS), L-glutathione reduced (GSH), sodium diethyldithiocarbamate trihydrate, and methyl thioglycolate (MTG) were from Sigma-Aldrich (Taufkirchen, Germany). 2,2'-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044) was purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). All other commonly used chemical reagents and buffer components were from Applichem (Darmstadt, Germany) and Fisher Scientific (Reinach, Switzerland).

2-Chlorotrityl resin, O-benzotriazole-N,N,N,N′-tetramethyl-uronium-hexafluoro-phosphate (HBTU), and Fmoc-protected amino acids were purchased from GL Biochem (Shanghai, China) Ltd. All solvents were purchased of analytical grade from Merck. Piperidine, trifluoroacetic acid (TFA), N,N-diisopropyl ethyl amine (DIPEA), and triisopropyl silane (TIPS) were from Acros (Milan, Italy). Sodium dihydrogen phosphate and disodium hydrogen phosphate were from BDH AnalaR (Milan, Italy). High-purity Milli-Q-water (MQ water) with a resistivity greater than 18 MΩ·cm was obtained from an in-line Millipore RiOs/Origin system.

Succinic anhydride and o-dichlorobenzene were purchased from Sigma-Aldrich (St. Louis, MO, USA). Mono-Fmoc ethylenediamine was purchased from Combi-Blocks (San Diego, CA, USA). N,N,N′,N′-tetramethyl-O-(1H-benzotriazol-1-yl)uronium hexafluorophosphate, O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HBTU) and all protected amino acids for peptide synthesis were purchased from Anaspec (Fremont, CA, USA). N,N-Diisopropylethylamine (DIPEA) was purchased from MP Biomedicals, LLS (Solon, OH, USA. Dimethylformamide (DMF), dichloromethane (DCM) and piperidine were purchased from Fisher Scientific (Pittsburgh, PA, USA). Gd₃N@C80 was purchased from SES Research (Houston, TX, USA). Maleimide-opfp (pentafluorophenyl 3-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)propanoate) was synthesised according to a reported protocol^{13 (link)}.