Challenging SPPS: Difficult sequences and side reactions

Peptide therapeutics have seen increased interest in the last decade, making peptide synthesis a critical step in the drug discovery and development process. One of the major drawbacks in peptide synthesis is that success largely depends on the peptide sequence being synthesized, so what do you do when you have a sequence with failed couplings at certain cycles? Do you extend the coupling time? Change reagents? Do multiple couplings? Here we’ll discuss our take on these questions using fast parallel synthesis optimization of a sterically hindered model peptide, Aib-ACP (VQ-Aib-Aib-IDYING-NH2) which saw improvements from 7.8% using HCTU to 91% using COMU and increasing the reaction temperature to 75 °C with short reaction times (2 x 3 min). What if your synthesis challenges aren’t difficult couplings but side reactions? We’ll discuss strategies for minimizing their occurrence during fast SPPS.