Mironova Labs · Protocol

Lipidation / Linker Attachment Protocol

Fatty diacid–spacer conjugation to lysine for long-acting peptides

DMTMM·Cl (mixed solvent) or DMTMM·BF₄ (organic phase)GLP-1 class peptide modification, side-chain acylation, PEG-handle attachment

Reagents

Reagent	Role	Amount
Fatty diacid–spacer construct (e.g., C18 or C20 linker)	Acyl donor	1.5–2.0 eq
DMTMM salt	Coupling reagent	1.5–2.5 eq
NMM	Base	3.0–5.0 eq
Peptide with free ε-lysine	Nucleophile	1.0 eq

Conditions

Solvent

DMF, DMF/water (9:1–4:1), or aqueous buffer for Cl; neat DMF for BF₄

Temperature

0–25 °C (lower temperatures reduce over-acylation)

Reaction Time

2–8 h

Atmosphere

Ambient or N₂

Procedure

1
If peptide has multiple free amines, ensure orthogonal protection so that only the target ε-lysine is available for acylation.
2
Dissolve fatty diacid–spacer construct (1.5–2.0 eq) in DMF or DMF/water mixture at 0–10 °C.
3
Add DMTMM salt (1.5–2.5 eq) and NMM (3.0–5.0 eq). Stir for 5–10 min to pre-activate the carboxyl group.
4
Add the peptide (1.0 eq, dissolved in minimum DMF or buffer) to the activated acid solution.
5
Stir at 0–25 °C for 2–8 h. Monitor by analytical HPLC.
6
Quench by dilution with cold water or buffer. Purify by preparative HPLC.

Expected Outcome

Selective mono-acylation of target lysine with minimal over-acylation. Clean HPLC profile suitable for downstream processing. Reproducible impurity profile across batches.

Analytical Monitoring

Analytical RP-HPLC (C18, gradient). LC-MS for identity confirmation. Monitor for di-acylated species and triazine adducts.

Troubleshooting

Over-acylation (di-acylated product)

Reduce DMTMM equivalents to 1.2 eq. Lower temperature to 0 °C. Reduce reaction time. Ensure orthogonal protection of non-target amines.

Low conversion

Increase DMTMM equivalents. Extend reaction time. Ensure fatty acid is fully dissolved (add DMSO if needed for solubility).

Triazine adduct detected

Reduce DMTMM excess. This side product is typically separable by prep HPLC but is best minimized at the reaction level.

Notes

These conditions are chemically plausible extrapolations from general DMTMM amide coupling data. No published study has specifically demonstrated DMTMM for GLP-1 peptide lipidation at manufacturing scale. Users should treat this as an evaluation starting point.
For semaglutide-class molecules, the lipidation step is quality-critical. Coupling-reagent choice directly affects the impurity profile.
DMTMM mechanistically avoids the guanidinylation risk inherent to HATU/HBTU at this step.
Batch-to-batch reagent purity (≥99%) is important for reproducible impurity profiles at scale.