Just Add Water:  A New Fluorous Capping Reagent for Facile Purification of Peptides Synthesized on the Solid Phase

Abstract

A novel fluorous capping reagent is introduced to facilitate purification during solid-phase peptide synthesis (SPPS). Reagent 1 is a trivalent iodonium salt that reacts vigorously with free amines to deliver a long-chain fluoroalkyl group. It has been used to tag all unreacted amines following the peptide coupling step in SPPS. The resulting fluoroalkylated amine is no longer able to couple in further peptide coupling steps and is also stable to standard peptide synthesis conditions. Deletion products are removed using flash fluorous chromatography to yield the pure, full-length peptide.

Highly fluorinated amphiphilic molecules and self-assemblies with biomedical potential

“…Applications of fluorous chemistry to the synthesis of peptides and protein sequences are illustrated by endcapping of a peptide with an F-chain tag, using an F-alkylated trivalent iodonium salt as reagent, in order to facilitate product removal and purification [37].…”

A Fluorous Capping Strategy for Fmoc‐Based Automated and Manual Solid‐Phase Peptide Synthesis

“…The fluorous-tagged deletion products tend to precipitate out of aqueous solutions, and the supernatant contains mostly the desired product. We have noted previously, that for longer peptides passage through fluorous silica gel may sometimes be necessary [7] but for the shorter peptides employed here, mere centrifugation is enough to remove most unwanted products.…”

“…The more promising of these approaches have been the introduction of handles that provide an avenue for the facile removal of unwanted products, mainly those due to failed couplings. [4][5][6] We and others have demonstrated the use of fluorous capping during solid-phase synthesis of peptides, [7][8][9] oligonucleotides, [10] and carbohydrates. [11][12][13][14][15] In addition, fluorous compounds and solvents have found use in protein design, [16][17][18][19][20][21][22][23][24][25][26][27] reaction acceleration, [28] catalysis, [29][30][31][32][33][34] combinatorial chemistry, [35] proteomics [36] and organic separation methodology.…”

“…[34,[37][38][39][40][41][42][43][44][45] by use of fluorous technology comprised treating the solid support with reagent 1, which caps all unconsumed residual terminal amines resulting from incomplete reaction that may participate in further couplings steps, giving rise to undesired deletion products. [7] The fluoroalkyl tag (R f CH 2 -) appended in this manner renders amines unreactive in all subsequent steps of peptide synthesis. At the termination of the synthesis, the crude peptide can then be purified by simple centrifugation or by fluorous flash chromatography, which results in the removal of all tagged deletions (Figure 1).…”

“…[7] This work was motivated by the need to make our strategy general and establish the utility of trivalent iodonium salts as robust capping reagents during routine Fmoc synthesis.…”