Fmoc-Arg-OH.HCl

This plan is based on literature, please modify it to meet your specific needs.
SPPS of linear vasopressin^[1]
Linear vasopressin syntheses were performed in glass syringes equipped with a polyethylene porous disc and attached to a vacuum manifold for the removal of excess reagents and solvents.
1. Add 0.3g of pre-loaded Fmoc-Gly-Rink amide resin (loading capacity of 0.5mmol/g) into 3mL of NBP/DMC (8/2; v/v) mixed solvent. After standing and swelling, filter to remove the solvent.
2. Add 1.5mL of NBP/DMC containing 20% piperidine (PIP) or diethanolamine (DEAPA) to the swollen resin and shake and invert at room temperature for 15min (2 times).
3. Wash the resin with 1.5mL of NBP/DMC (3 times; 2min each).
4. Pre-activate Fmoc-Arg-OH.HCl and other Fmoc-amino acid derivatives (2 equivalents; 0.3mmol) with Oxyma Pure (2-5 equivalents; 0.3-0.75mmol) and DIC (2 equivalents; 46.4μL; 0.3mmol) for 5min, then couple with the resin. After each step of coupling, treat the peptide resin with 1.5mL of NBP/DMC containing 20% piperidine (PIP) or diethanolamine (DEAPA) (2 times; 15min each), and then wash with 1.5mL of NBP/DMC (3 times; 2min each). 
5. After Fmoc cleavage at the N-terminal amino group, further wash the peptide resin with 1.5mL of DCM (3 times; 2min each) under vacuum and dry for 12h.
6. Dissolve the dried peptide resin in 3mL of TFA/TIS/H₂O (95/2.5/2.5; v/v/v) mixed solution and stir for 2h. Then filter the resin, wash with 1mL of TFA for 1min.
7. Slowly add 10mL of cooled to 4°C diisopropyl ether to the system, filter the peptide product and vacuum dry to obtain crude linear vasopressin, which is directly analyzed by HPLC-MS.

References:
[1] Fantoni T, Orlandin A, Di Stefano I, et al. Solid phase peptide synthesis using side-chain unprotected arginine and histidine with Oxyma Pure/TBEC in green solvents. Green Chem. 2024;26(21):10929-10939.