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Fmoc-N-Me-Ser(tBu)-OH is a protected N-methyl-L-serine building block. The serine hydroxyl is masked as a tert-butyl ether, while the backbone amino nitrogen carries both the Fmoc group and the methyl substituent that remains in the final peptide.
Its experimental value comes from backbone N-methylation, not from changing the serine side chain. Compared with Fmoc-Ser(tBu)-OH, the final residue loses one backbone N-H donor and gains steric bulk directly at the peptide bond.
Product Information
| Product Name | Fmoc-N-Me-Ser(tBu)-OH |
| Catalog No. | AS2092 |
| CAS No. | 197632-77-2 |
| Molecular Formula | C23H27NO5 |
| Molecular Weight | 397.46 g/mol |
| Building Block Type | Fmoc-protected N-methyl-L-serine with O-tert-butyl protection |
| Primary Applications | Backbone N-methylation; conformational peptide SAR; modified Fmoc-SPPS; macrocyclic and permeability-focused peptide design |
Why N-Methyl Serine Changes Peptide Behavior
Backbone N-methylation can alter local conformation, hydrogen-bonding patterns, protease recognition and, in some constrained peptide systems, permeability. The effect is highly position-dependent. We consider matched analog comparison more informative than assuming N-methylation is universally beneficial.
Coupling Is Often More Demanding
N-methylated amino acids are sterically hindered relative to ordinary amino acids. Incomplete coupling can create deletion impurities that become difficult to remove after several additional cycles. For difficult sequences, the practical issues overlap with the incomplete-coupling risks described in Common Side Reactions in SPPS.
Protecting-Group Logic
The side-chain hydroxyl remains tBu-protected during normal Fmoc cycles and is regenerated during final acidic cleavage. The reagent is therefore compatible with the Fmoc/tBu concept, but the N-methyl group makes its coupling behavior different from standard serine.
Procurement and QC
Confirm CAS 197632-77-2, formula C23H27NO5, MW 397.46 g/mol and L stereochemistry. LC-MS verifies composition but does not by itself prove enantiomeric purity.
If a sequence contains several N-methyl residues or other sterically demanding monomers, route feasibility should be evaluated before synthesis begins. Alan Scientific can incorporate these residues through custom noncanonical peptide synthesis.
Product Documents
A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.
Certificates of Analysis (COAs) are batch-specific. Please contact us to request the COA for your product, and we will provide it by email.
Frequently Asked Questions
Is this the same as Fmoc-Ser(tBu)-OH?
No. This reagent installs backbone N-methyl serine; ordinary Fmoc-Ser(tBu)-OH does not.
What remains after final deprotection?
The Fmoc and tBu groups are removed, while the backbone N-methyl substituent remains.
Why can coupling be difficult?
N-methyl substitution increases steric demand at the reacting amino-acid center.
Related Technical Resources
Read how noncanonical residues change peptide design
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