ABSTRACT
A broadly applicable one-pot methodology for the facile transformation of linear peptides into tetracyclic peptides through a chemoenzymatic peptide synthesis/chemical ligation of peptides onto scaffolds/copper(I)-catalyzed reaction (CEPS/CLIPS/CuAAC; "triple-C") locking methodology is reported. Linear peptides with varying lengths (≥14 amino acids), comprising two cysteines and two azidohomoalanines (Aha), were efficiently cyclized head-to-tail by using the peptiligase variant omniligase-1 (CEPS). Subsequent ligation-cyclization with tetravalent (T41/2 ) scaffolds containing two bromomethyl groups (CLIPS) and two alkyne functionalities (CuAAC) yielded isomerically pure tetracyclic peptides. Sixteen different functional tetracycles, derived from bicyclic inhibitors against urokinase plasminogen activator (uPA) and coagulation factor XIIa (FXIIa), were successfully synthesized and their bioactivities evaluated. Two of these (FF-T41/2 ) exhibited increased inhibitory activity against FXIIa, compared with a bicyclic control peptide. The corresponding hetero-bifunctional variants (UF/FU-T41/2 ), with a single copy of each inhibitory sequence, exhibited micromolar activities against both uPA and FXIIa; thus illustrating the potential of the "bifunctional tetracyclic peptide" inhibitor concept.
Subject(s)
Peptides, Cyclic/chemical synthesis , Peptides/chemistry , Alanine/analogs & derivatives , Alanine/chemistry , Amino Acid Sequence , Combinatorial Chemistry Techniques , Cyclization , Cysteine/chemistry , Factor XIIa/antagonists & inhibitors , Humans , Models, Molecular , Peptides, Cyclic/chemistry , Peptides, Cyclic/pharmacology , Urokinase-Type Plasminogen Activator/antagonists & inhibitorsABSTRACT
We report a one-pot ligation/cyclization technology for the rapid and clean conversion of linear peptides into tricyclic peptides that is based on using tetravalent scaffolds containing two benzyl bromide and two alkyne moieties. These react via CLIPS/CuAAC reactions with cysteines and azides in the peptide. Flexibility in the scaffolds is key to the formation of isomerically pure products as the flexible scaffolds T41 and T42 mostly promote the formation of single isomeric tricycles while the rigid scaffolds T43 and T44 do not yield clean products. There seems to be no limitation to the number and types of amino acids present as 18 canonical amino acids were successfully implemented. We also observed that azides at the peptide termini and cysteine residues in the center gave better results than compounds with the functional groups placed the other way round.
ABSTRACT
Enantiomerically pure 2,6-disubstituted piperidinones were synthesized from furfural involving an organocatalyzed Mannich reaction, aza-Achmatowicz reaction, and an N-acyliminium ion-mediated coupling step. This approach was also successfully applied to a total synthesis of (-)-sedacryptine and one of its epimers.
