Fmoc-Arg(pbf)-OH, with the CAS number 154445-77-9, is a highly versatile protected amino acid derivative widely used in peptide synthesis. Its full chemical name isNα-[(9H-fluoren-9-yl)methoxycarbonyl]-Nω-(2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl)-L-arginine. The molecular formula is C₃₉H₄₉N₅O₇S, and the molecular weight is 732.91 g/mol. This compound features a highly efficient orthogonal protecting group strategy, making it an indispensable building block in the construction of complex peptides and proteins.
Physically, Fmoc-Arg(pbf)-OH appears as a white to off-white crystalline powder. It has a melting point in the range of 135-140°C and exhibits good thermal stability under normal storage conditions. Chemically, it issparingly soluble in water but readily soluble in common organic solvents such as dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dichloromethane (DCM), making it highly suitable for solid-phase peptide synthesis (SPPS) protocols. The compound is optically active, with a specific rotation [α]²⁰/D typically ranging from -14.0° to -18.0° (in methanol, c=1), reflecting its L-configuration. It has low hygroscopicity and remains stable under neutral and weakly acidic conditions, but may undergo deprotection under strong acidic environments.
Its primary application lies insolid-phase peptide synthesis (SPPS). TheFmoc (9-fluorenylmethoxycarbonyl) group at the N-terminus is cleavable under mild basic conditions (e.g., 20% piperidine in DMF), which is a standard step in Fmoc-based SPPS. The Pbf (2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl) group serves as an acid-labile protecting group for the guanidinium side chain of arginine. It is stable under the basic conditions of Fmoc deprotection but is efficiently removed during the final cleavage step using strong acids like trifluoroacetic acid (TFA).
In pharmaceutical research, Fmoc-Arg(pbf)-OH is extensively used to synthesize a wide range of bioactive peptides, includingpeptide hormones, enzyme inhibitors, antimicrobial peptides, andtherapeutic vaccines. The use of the Pbf protecting group is particularly advantageous as it minimizes side reactions during peptide chain assembly, such as aspartimide formation and guanidinium group modification, thereby ensuring the high purity and structural integrity of the final peptide product. It is also a key intermediate in the production of peptide-based drugs targeting various diseases, including cancer, diabetes, and infectious diseases.
Safety-wise, this compound is considered stable and non-toxic under normal handling conditions. However, as with all fine chemicals, proper precautions should be taken. It should be stored in asealed, cool, and dry environmentat 2-8°C, away from strong acids, strong oxidizing agents, and moisture to prevent premature deprotection or degradation.
In summary,Fmoc-Arg(pbf)-OH is an indispensable tool in modern medicinal chemistry and peptide science, enabling the efficient and high-fidelity construction of arginine-containing peptides with precise control over protecting group chemistry and final product purity.
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