Amino acid derivatives and SPPS building blocks
Fmoc and Boc protected amino acids, pseudoproline dipeptides, phosphorylated and unnatural derivatives, and pre-activated forms for SPPS. Lot-enantiomeric purity at the monomer propagates into the final peptide—especially on long sequences.
99.5–99.9%
ee / L-content (typical COA)
Fmoc / Boc
protection strategies
D & L
configured supplies
g–kg
building block scale
Chiral
HPLC or CE on request
Enantiomeric purity propagation
Each coupling step multiplies stereochemical risk. A 0.5% D-content in a single Fmoc-L-amino acid does not stay localized—it distributes across epimeric related substances after synthesis.
For a 20-mer synthesized entirely from 99.5% L-amino acids, naive propagation suggests roughly percent-level cumulative epimer burden unless purification removes epimers. Tightening monomer to 99.8% L-content reduces the epimer pool and is common for API-bound SPPS.
Indicative L-content vs mer length
Simplified illustration assuming independent 0.5% or 0.2% D-incorporation per residue and no chiral purification. Actual epimer maps are sequence-dependent.
| Monomer L-content | 20-mer (approx. epimer burden) | 40-mer | 60-mer |
|---|---|---|---|
| 99.5% (0.5% D per coupling) | ~9–10% epimerized positions (statistical) | ~18% | ~26% |
| 99.8% (0.2% D per coupling) | ~4% | ~8% | ~11% |
| API practice | Prefer ≥99.8% for long peptides | Chiral monitoring on critical residues | Document supplier COA on MF |
Figures are indicative industry-typical values. Lot- and project-specific data appear on the quotation and certificate of analysis.
Derivative classes supplied
Standard Fmoc amino acids
- All 20 proteinogenic L-amino acids (tBu, Trt, Pbf protections)
- Fmoc-Cys(Trt), Fmoc-His(Trt), Fmoc-Arg(Pbf)
Difficult couplings
- Pseudoproline dipeptides
- Dimethyl-Lys, isoacyl dipeptides
- Pre-activated Fmoc-AA-OPfp / -OSu forms
Unnatural & D-amino acids
- N-methyl, β-amino, Aib
- D-configured for protease-stable sequences
PTM building blocks
- Phospho Fmoc amino acids
- Methylated Arg/Lys derivatives
Typical trace impurities on COA
Peptide manufacturers audit these on incoming amino acids to avoid colored coupling solutions and failed API specs.
Acetate (counter-ion)
0.1–1.0% w/w (typical reported)
From salt exchange or crystallization
Free amino acid
<0.1–0.5%
Deprotection or hydrolysis
Ethyl acetate (residual)
ppm–low %
Process solvent; ICH Q3C mindset
Water
0.1–1%
Karl Fischer
Heavy metals
Low ppm bands
Catalyst residues from synthesis
Chiral purity
99.5–99.9% L
CE or chiral HPLC
Figures are indicative industry-typical values. Lot- and project-specific data appear on the quotation and certificate of analysis.
How peptide teams qualify lots
Receipt vs master spec
Compare COA to internal amino acid specification.
Identity and chiral release
Spot-check new vendors with in-house chiral method.
Solution color / clarity
Dissolve in DMF for SPPS; reject lots with unexpected hue.
Warehouse conditions
Cool, dry, desiccated; retest dating per supplier stability.
Deliverables
- Protected amino acid with lot COA
- Chiral purity and identity data
- Residual solvent and water where listed
- MSDS and storage guidance
- Custom specs for API manufacturers (quoted)
Frequently asked questions
For peptides longer than ~30 residues, for API release with chiral limits, or when a single epimer peak is a qualified impurity.
Related
Custom Peptide Synthesis
Solid-phase and solution synthesis of linear and modified peptides for discovery, assay development and lead optimization. Scale, purity tier and QC depth are matched to how the material will be used—not every program needs the same finishing step.
View detailsGMP Peptide API
GMP-manufactured peptide drug substance for clinical trials and commercial demand under a quality system aligned to ICH and regional GMP expectations. Scope is drug substance—synthesis, purification, isolation, release and stability—not discovery-grade custom work.
View detailsPeptide Modifications
Terminal caps, cyclization, stapling, PTMs, fluorescent and affinity tags, PEG/lipid appendages and unnatural backbones—installed during SPPS or in solution after the chain is built. Each class changes synthesis time, purification and how the product should be specified on the COA.
View detailsPeptide NCE / CMC Development
Process and analytical development that connects research synthesis to a repeatable drug substance story: route selection, impurity fate, specification rationale and stability—structured phase by phase from preclinical supply through commercial readiness.
View detailsReady to specify this for your program?
Share sequence, scale and documentation needs. We reply with indicative specs and a project-specific quotation.