Fmoc-D-Asn(Trt)-D-Thr(psi(Me,Me)pro)-OH is an Fmoc-protected stereochemically defined D-Asn-D-Thr pseudoproline building block for solid-phase peptide synthesis (SPPS). The D-Thr residue is incorporated in a reversible 2,2-dimethyloxazolidine pseudoproline form that temporarily changes local backbone hydrogen-bonding and conformation during chain elongation.

The preformed D-Asn-D-Thr unit introduces the sequence motif in one coupling operation. Under standard TFA-mediated final cleavage and deprotection, the acid-labile pseudoproline ring is opened and the native D-Thr residue is regenerated.

Product Information

Stereochemical Role in D-Residue Sequences

This building block is intended for sequences that specifically require the D-Asn-D-Thr stereochemical pattern. The D configuration should be treated as part of the product identity, not as an interchangeable naming variant of the corresponding L-residue pseudoproline reagent. This should be considered alongside aggregation control in SPPS when diagnosing sequence-dependent assembly problems.

Backbone Disruption During Assembly

The downstream D-Thr pseudoproline provides the same general synthetic concept used in L-series pseudoproline chemistry: a temporary oxazolidine interrupts local backbone hydrogen-bonding and conformation during Fmoc-SPPS. Its value remains sequence-dependent and should be assessed from actual assembly behavior.

Side-Chain Protection and Final Cleavage

The upstream D-Asn(Trt) protection is maintained during chain elongation while the downstream pseudoproline modifies the backbone. Final acid treatment is expected to remove the acid-labile side-chain protection and open the pseudoproline ring. The full cleavage formulation should be selected for the complete target sequence.

Sequence Planning

We would select this reagent only when the target design requires the D-Asn-D-Thr configuration and there is a synthetic reason to use a pseudoproline at that position. The effects of D-residue incorporation on peptide properties, including protease resistance, depend on the complete sequence and require experimental evaluation. Related motifs can be compared in the Ser/Thr pseudoproline building blocks.

Experimental Planning

For D-Asn-D-Thr-containing designs, verify the intended D/L configuration before ordering and before sequence entry into synthesis software. Pseudoproline placement should then be considered together with chain length, resin loading, hydrophobicity, and the point at which coupling or deprotection performance begins to decline.

For projects where building-block selection needs to be evaluated with the full target sequence, our difficult peptide project support can support integrated planning, synthesis, purification, and QC requirements.

Product Documents

MSDS - Fmoc-D-Asn(Trt)-D-Thr(psi(Me,Me)pro)-OH (AS4117)

The Safety Data Sheet provides product identification, hazard information, handling and storage guidance, exposure controls, transport information, and regulatory information for laboratory use.

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

What does psi(Me,Me)pro indicate?

It denotes a dimethyl-substituted pseudoproline formed from the downstream D-Thr residue. The five-membered oxazolidine temporarily changes backbone behavior during synthesis.

Why is the D-Asn-D-Thr unit supplied as a preformed building block?

The amide bond immediately before the pseudoproline nitrogen is already formed, avoiding direct acylation of a sterically hindered oxazolidine nitrogen and allowing the motif to be introduced in one coupling operation.

Does the pseudoproline remain in the final peptide?

No. Standard TFA-mediated final cleavage opens the pseudoproline ring and restores the downstream D-Thr residue.

Can the corresponding L-series reagent be substituted?

Not when the design specifically requires the D-Asn-D-Thr stereochemistry. D/L configuration is part of the molecular identity and should be selected according to the target sequence.

Research Use Only.