FMOC-Arg(Pbf)-OH is an arginine derivative in which the amino group is protected by an Fmoc (9-fluorenylmethyloxycarbonyl) group and the guanidino group is protected by a Pbf (2,2,4,6,7-pentamethyl-dihydrobenzofuran-5-sulfonyl) group. Its properties, characteristics, and applications are described as follows:

I. Properties:

Physical Properties:

FMOC-Arg(Pbf)-OH typically appears as a white to off-white solid with a melting point of approximately 132°C. Its specific optical rotation is −5.5º (c = 1, DMF), and its density is around 1.37 ± 0.1 g/cm³. It is slightly soluble in organic solvents such as DMF, DMSO, and methanol. The acid dissociation constant (pKa) is approximately 3.83 ± 0.21.

Chemical Properties:

The molecule contains both a protected amino group and a protected guanidino group. Under specific acidic conditions, the Fmoc and Pbf protecting groups can be selectively removed to release the free amino and guanidino groups, which can then participate in subsequent chemical reactions.

II. Characteristics:

Selective Protection:

The Fmoc and Pbf protecting groups provide selective protection for the amino and guanidino groups of arginine, respectively. This prevents unwanted side reactions during peptide synthesis or other chemical reactions, thus improving the reaction selectivity and yield.

Good Stability:

FMOC-Arg(Pbf)-OH exhibits good chemical stability under ambient and standard storage conditions, which facilitates long-term storage and transportation. However, it should be protected from strong acids, strong bases, or reactive chemicals to prevent premature deprotection or structural degradation.

High Operability:

Thanks to its partial solubility in common organic solvents, FMOC-Arg(Pbf)-OH is easy to handle and can be conveniently used in both solution-phase and solid-phase organic synthesis reactions.

III. Applications:

Peptide Synthesis:

FMOC-Arg(Pbf)-OH is a commonly used amino acid monomer in peptide synthesis, particularly well-suited for solid-phase peptide synthesis (SPPS). By sequentially coupling various protected amino acids, peptides containing arginine residues can be synthesized and further used in the preparation of bioactive peptide drugs, peptide-based vaccines, and more.

Biomedical Research:

With inherent bioactivity, FMOC-Arg(Pbf)-OH features a positively charged arginine residue that can interact selectively with other biomolecules. It is useful in the study of cell signaling, protein–protein interactions, and other biological processes. Moreover, it holds potential as an antibacterial, antiviral, and anticancer agent. For instance, it can disrupt bacterial membranes through electrostatic interactions or interfere with tumor cell growth and proliferation pathways, making it applicable in cancer treatment, diagnostics, or tumor imaging.

Materials Science:

The diverse functional groups of the arginine side chain can interact specifically with various material surfaces, making FMOC-Arg(Pbf)-OH suitable for surface modification and functionalization. It can be used to develop materials with improved biocompatibility, specific binding, or adsorption properties, useful in medical devices, biosensors, or advanced coatings.

Overall, FMOC-Arg(Pbf)-OH is a versatile compound widely used in peptide chemistry, biomedical science, and materials engineering, owing to its selective protection, chemical stability, and biological relevance.