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Fmoc-AzaTrp-OH (Fmoc-L-7-azatryptophan, also known as (S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-(1H-pyrrolo[2,3-b]pyridin-3-yl)propanoic acid) is a specialized Fmoc‑protected amino acid building block that incorporates an aza‑indole ring system in place of the standard indole side chain of tryptophan. The Fmoc protecting group at the N‑terminus enables seamless integration into standard Fmoc SPPS workflows, while the 7‑azatryptophan moiety introduces a nitrogen atom into the indole ring that significantly alters the electronic and hydrogen‑bonding properties of the side chain.

Boc-Pip(Fmoc)-OH (4-(Boc-amino)-1-Fmoc-piperidine-4-carboxylic acid, CAS 368866-07-3) is a conformationally constrained unnatural amino acid derivative built upon a piperidine ring system. The molecule features a piperidine-4-carboxylic acid core with two orthogonal protecting groups: a tert-butoxycarbonyl (Boc) group protecting the 4-amino nitrogen, and a 9-fluorenylmethoxycarbonyl (Fmoc) group protecting the ring nitrogen at the 1-position.

Fmoc-Sar-OH.H2O is the Fmoc‑protected form of sarcosine (N‑methylglycine), supplied as the monohydrate crystalline form. Sarcosine is the simplest N‑alkylated amino acid, featuring a secondary amino group (—NH—) in place of the primary amino group found in standard α‑amino acids. This structural difference fundamentally alters the conformational behavior of sarcosine‑containing peptides: the N‑methyl group restricts backbone flexibility, reduces the propensity for hydrogen‑bonding, and imparts unique secondary structure preferences not accessible with conventional amino acid residues.

Fmoc-N-Me-Trp(Boc)-OH (N-α-(9-Fluorenylmethoxycarbonyl)-N-α-methyl-N-in-tert-butoxycarbonyl-L-tryptophan, CAS 197632-75-0) is a di-protected N-methylated tryptophan derivative designed for Fmoc-based solid-phase peptide synthesis (SPPS). The molecule incorporates three key structural features: an Fmoc group protecting the α-amino function, an N-methyl group at the α-nitrogen, and a Boc group protecting the indole nitrogen of the tryptophan side chain.

Fmoc-Asp(OMpe)-OH (N-α-Fmoc-L-aspartic acid β‑3‑methylpent‑3‑yl ester) is an Fmoc‑protected L‑aspartic acid derivative bearing the sterically demanding β‑3‑methylpent‑3‑yl (OMpe) side‑chain protecting group. The compound was specifically developed as an advanced alternative to the standard Fmoc‑Asp(OtBu)‑OH for use in Fmoc solid‑phase peptide synthesis (SPPS), where repetitive piperidine treatment during Fmoc deprotection can otherwise trigger extensive aspartimide‑related by‑product formation at aspartyl residues, particularly in Asp‑Gly, Asp‑Ser, and Asp‑Thr sequences.

Fmoc-TmbGly-OH is a specialized dual‑protected glycine derivative featuring a 2,4,6‑trimethoxybenzyl (Tmb) group on the backbone amide nitrogen, in addition to the standard base‑labile Fmoc protecting group on the terminal amine. This structural innovation positions Fmoc-TmbGly-OH as a member of the benzyl‑based backbone protecting group family, which includes the 2,4‑dimethoxybenzyl (Dmb) and 2‑hydroxy‑4‑methoxybenzyl (Hmb) analogues. In the native Fmoc solid‑phase peptide synthesis (SPPS) of glycine‑containing peptides, the high conformational flexibility of glycine makes peptide chains prone to intermolecular aggregation on solid supports — leading to incomplete deprotection, slow coupling kinetics, and ultimately low crude peptide yields and purities. Fmoc-TmbGly-OH addresses this challenge through strategic backbone protection that disrupts hydrophobic aggregation during chain assembly, while its enhanced acid lability (cleaved with as little as 7% TFA) marks a strategic upgrade from Fmoc-(Dmb)Gly-OH, enabling selective orthogonal deprotection for complex, high‑value peptide targets.