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Four 14-residue peptides have recently been linked to a cavitand containing methyl feet, to develop a de novo protein with a hydrophobic template. The synthetic use of phosphate-footed cavitands is demonstrated through the reaction of suitably activated peptides with phosphate-footed bromomethyl and phosphate-footed thiomethyl cavitands, which form the de novo protein with links to a hydrophilic template.

Sortase A (SrtA)-mediated ligation has emerged as an attractive tool in bioorganic chemistry attributing to the remarkable specificity of the ligation reaction and the physiological reaction conditions. However, the reversible nature of this reaction limits the efficiency of the ligation reaction and has become a significant constraint to its more widespread use. We report herein a novel set of SrtA substrates (LPETGG-isoacyl-Ser and LPETGG-isoacyl-Hse) that can be irreversibly ligated to N-terminal Gly-containing moieties via the deactivation of the SrtA-excised peptide fragment through diketopiperazine (DKP) formation. The convenience of the synthetic procedure and the stability of the substrates in the ligation buffer suggest that both LPETGG-isoacyl-Ser and LPETGG-isoacyl-Hse are valuable alternatives to existing irreversible SrtA substrate sequences.