Piperidine

All solvents and reagents used were purchased from commercial sources and used without further purification. Fmoc-Ala-OH, Fmoc-Pro-OH, Fmoc-Trp (Boc)-OH, Fmoc-His (Trt)-OH, Fmoc-Leu- OH, Fmoc-Ser(tBu)-OH, Fmoc-Gln (Trt)-OH, Fmoc-Tyr (tbu)-OH, Fmoc-Arg (Pbf)-OH, Fmoc- Thr (tBu)-OH and Oxyma-Pure were ordered from Novabiochem (Millipore Sigma Corporation2,2,2-Trifluoroethanol (TFE), Dichloromethane (DCM), Dimethylformamide (DMF), Acetonitrile and Diethyl Ether (Et2O) were ordered from Fisher Scientific (Hampton, NH, United States). Trifluoroacetic acid (TFA), Diisopropylethylamine (DIPEA) and Piperidine were ordered from Chem-Impex International (Wood Dale, IL, United States). Amiodarone HCL, 3-(Tritylthio) propionic acid, Ethanedithiol (EDT), Triisopropylsilane (TIPS), 3-chloropropanethiol, 1,2,2,6,6- PentamethylPiperidine and Sodium Iodide were ordered from Sigma-Aldrich (St. Louis, MO, United States). 2-(1H-Benzotriazole-1-yl)-1,1,3,3-tetramethylaminium tetrafluoroborate (TBTU) and 1- Hydroxybenzotriazole hydrate (HOBt) were ordered from P3 Biosystems (Louisville, KY, United States)., St. Louis, MO). Rink amide MBHA resin was ordered from vivitide, LLC (Garder, MA, United States).

All chemicals were purchased from Sigma-Aldrich (St. Louis, MO, USA) or Fisher Scientific (Hampton, NH, USA) unless otherwise specified. Amine terminated ethylenediamine core generation 5 poly(amidoamine) dendrimer (G5(NH₂)₁₂₈) was obtained from Dendritech, Inc. (Midland, MI, USA). POL3026 peptide was synthesized by CPC Scientific (Sunnyvale, CA, USA) with >95% purity. Piperidine, diisopropylethylamine (DIPEA), N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), and 1-hydroxybenzotriazole (HOBt) were obtained from ChemImpex International Inc. (Wood Dale, IL, USA). ¹¹¹InCl₃ (t_1/2 = 2.81 days) and DOTA-NHS-ester were acquired from Nordion (Ottawa, ON, Canada) and Macrocyclics (Plano, TX, USA), respectively. Fmoc-N-PEG₂₀₀₀-NHS-ester and mPEG₂-NHS-ester were purchased from Creative Pegworks (Chapel Hill, NC, USA) and Quanta Biodesign (Plain City, OH, USA), respectively. All reagents and solvents were used as received without further purification.

All solvents required for synthesis, including ethanol, methanol, acetone, acetonitrile (ACN), tetrahydrofuran (THF), petroleum spirit, chloroform, dichloromethane (DCM), N-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF), were purchased from Merck and ChemSupply Pty (Aust.). Special reagents for the solid phase peptide synthesis (SPPS), i.e., piperidine, diisopropyl carbodiimide (DIC), diisopropylethylamine (DIPEA), acetic anhydride, Oxyma Pure (ethyl cyanohydroxyiminoacetate), trifluoroacetic acid (TFA) and triisopropyl silane (TIPS), were purchased from various suppliers - Chem-Impex Inc., Novabiochem^®, Sigma-Aldrich Pty Ltd. and Thermo Fisher Scientific. Solid bed support (Rink amide AM and Wang resin) having 0.3–0.6 mmol/g loading, and Fmoc-protected amino acids were purchased from Chem-Impex Inc. and P3Biosystems.