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Fmoc-D-Arg(Pbf)-OH (N-α-Fmoc-Nω-(2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl)-D-arginine) is a D-configured arginine derivative featuring a Pbf (2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl) side‑chain protecting group. Structurally, the molecule contains a guanidinium side chain essential for arginine‘s biological function — mediating hydrogen bonding and electrostatic interactions critical for protein‑protein and protein‑nucleic acid recognition — rendered inert during peptide assembly by the bulky, electron‑rich Pbf group.

Fmoc-D-4-Nitro-Phe-OH (N-α-fluorenylmethoxycarbonyl-4-nitro-D-phenylalanine) is a D-configuration, Fmoc-protected phenylalanine derivative featuring an electron-withdrawing nitro group at the para position of the aromatic ring. The D-amino acid configuration is particularly significant, as D-amino acids incorporated into peptides confer enhanced proteolytic stability and distinct conformational properties compared to their L-counterparts—features widely exploited in the design of therapeutic peptides, peptidomimetics, and drug discovery libraries.

Fmoc-Tranexamic acid (trans-4-(Fmoc-aminomethyl)cyclohexane-1-carboxylic acid) is a specialized Fmoc-protected synthetic amino acid derivative incorporating the trans-4-aminomethylcyclohexane-1-carboxylic acid scaffold—the core structure of the clinically approved antifibrinolytic agent tranexamic acid. The rigid, conformationally constrained cyclohexane ring in Fmoc-Tranexamic acid adopts the trans configuration, positioning the aminomethyl and carboxylic acid functionalities on opposite sides of the cyclohexane ring.

The product Fmoc-Lys(Mtt)-OH (Nα-Fmoc-Nε-4-methyltrityl-L-lysine, CAS 167393-62-6) is a specialized lysine derivative incorporating two orthogonal protecting groups. The molecule features the standard amino acid lysine backbone, with the α-amine protected by the base-labile 9-fluorenylmethyloxycarbonyl (Fmoc) group, and the side-chain ε-amine protected by the very acid-sensitive 4-methyltrityl (Mtt) group. This orthogonal protection strategy creates a powerful synthetic tool: the Fmoc group is cleaved under mild piperidine conditions (standard in Fmoc SPPS), while the Mtt group can be selectively removed under extremely mild acidic conditions (as low as 1% TFA in DCM) without affecting the Fmoc group or other standard protecting groups such as tBu or Boc.

Fmoc-Trp(Boc)-OH (N-α-Fmoc-N(in)-Boc-L-tryptophan) is a dual-protected tryptophan derivative featuring Fmoc protection of the α-amino group and a tert-butyloxycarbonyl (Boc) group on the indole side-chain nitrogen. Tryptophan residues present a well-documented challenge in Fmoc SPPS: the unprotected indole NH is susceptible to alkylation, oxidation, and the formation of unwanted colored by-products during coupling and deprotection steps.

Fmoc-Arg(Pbf)-OH (Nα-Fmoc-Nω-(2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl)-L-arginine, molecular formula C₃₄H₄₀N₄O₇S) is an N‑Fmoc‑protected and side‑chain‑protected derivative of the basic amino acid arginine, specifically designed for use in Fmoc solid‑phase peptide synthesis (Fmoc SPPS). Structurally, the molecule consists of a 9‑fluorenylmethyloxycarbonyl (Fmoc) group attached to the α‑amino nitrogen, and the guanidino side chain protected by the Pbf (2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl) group.