Solid-Phase Synthesis of Peptide Conjugates Derived from the Antimicrobial Cyclic Decapeptide BPC194

The solid-phase conjugation of the antimicrobial peptide c(KKLKKFKKLQ) (BPC194) to a linear or cyclic sequence through a 1,2,3-triazole ring is described. Cyclic alkynyl-peptidyl resins derived from BPC194 were treated with azidopeptides derived from the antimicrobial peptide BP100 or from the bacteriocin iturin A. The cyclic alkynyl-peptidyl resins incorporated at the 3-position a propargylglycine, a glutamic acid residue derivatized with propargylamine or a lysine bearing a propioloyl group. The reactions of the cyclic alkynyl resins with the BP100-derived azidopeptides depended on the length and the sequence of the azidopeptides. The reactions were performed by treatment of the alkynyl resin with CuI and ascorbic acid, and required the presence of piperidine/DMF or DIEA in 2,6-lutidine/DMF. The latter conditions also allowed the conjugation of the alkynyl-peptidyl resin bearing a propioloyl lysine to a linear or cyclic azidopeptide derived from the cyclic moiety of iturin A.