Evaluation of COMU as a coupling reagent for in situ neutralization Boc solid phase peptide synthesis

Abstract

Benzotriazole‐based coupling reagents have dominated the last two decades of solid phase peptide synthesis. However, a growing interest in synthesizing complex peptides has stimulated the search for more efficient and low‐cost coupling reagents, such as COMU which has been introduced as a nonexplosive alternative to the classic benzotriazole coupling reagents. Here, we present a comparative study of the coupling efficiency of COMU with the benzotriazole‐based HBTU and HCTU for use in in situ neutralization Boc‐SPPS. Difficult sequences, such as ACP(65–74), Jung–Redeman 10‐mer, and HIV‐1 PR(81–99), were used as model target peptides on polystyrene‐based resins, as well as polyethylene glycol‐based resins. Coupling yields obtained using fast in situ Boc‐SPPS cycles were determined with the quantitative ninhydrin test as well as via LC‐MS analysis of the crude cleavage products. Our results demonstrate that COMU coupling efficiency was less effective compared to HBTU and HCTU with HCTU ≥ HBTU > COMU, when polystyrene‐based resins were employed. However, when the PEG resin was employed in combination with a safety catch amide (SCAL) linker, more comparable yields were observed for the three coupling reagents with the same ranking HCTU ≥ HBTU > COMU. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.

COMU: scope and limitations of the latest innovation in peptide acyl transfer reagents

“…In the peptide field, COMU (16) is compatible with a broad range of solid supports, either PS-based or PEG-based, and the assembly of Boc-amino and Alloc-amino acids, where it is preferred over HCTU (6) [13,15,19,[21][22][23][24][25][26][27][28][29].…”

“…A drawback of COMU (16), like for other aminium/uronium salts, is that it is not suited for markedly slow couplings, such as cyclizations, because the N-terminal guanidylated peptide is obtained as a major product [50]. With regard to the efficiency of COMU (16) under fast acylation protocols, contradictory studies have been published [28,51]. On one hand, the Alewood group found no differences in coupling efficiency between COMU (16), HBTU (4), and HCTU (6) in Boc-SPPS using the in situ neutralization method and 1-min couplings, regardless of the type of resin used (although COMU 16 performed better in PEG-resins than PS-ones) [28].…”

High‐Throughput Synthesis of Peptide α‐Thioesters: A Safety Catch Linker Approach Enabling Parallel Hydrogen Fluoride Cleavage

“…The synthesis of SFTI‐1 ( 9 ) was performed on the aminomethyl‐PEG based resin ( 1‐ChemMatrix ) resulting in superior product quality. This resin has been used in our hands very successfully for difficult sequences28d as well as for the synthesis of selenocysteine‐containing α‐conopeptides 26. The ChemMatrix resin was pretreated in DMF overnight, and a sequence of three glycine residues was attached to improve the handling of the resin.…”

Synthesis of the Novel Covalent Cysteine Proteases Inhibitor with Iodoacetic Functional Group

“…Application of bromo-, chloro-, and iodoacetic acids in the peptide solid phase synthesis requires changes in the standard synthesis protocol [14]. The results demonstrate a comparison of standard synthesis involving DIC (N,N -diisopropylcarbodiimide) with HOBt (N-hydroxybenzotriazole), with the newer activation reagent like COMU (1-Cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylaminomorpholino-carbenium hexafluorophosphate) [15][16][17]. Synthesis yield and product purity were checked by mass spectrometry [18].…”