No abstract

A series of C2-arylated analogues of the diketopiperazine brevianamide F has been synthesized using a mild Pd-catalyzed CH-activation procedure. Biological evaluation of the new derivatives in different cell lines shows that this modification is responsible for the remarkable change in activity, turning a mild antibiotic and antifungal natural product (brevianamide F) into novel antitumoral compounds.Furthermore, the approach stated represents a new straightforward and versatile methodology with promising applications in peptidomimetics and medicinal chemistry.

The use of a triazene function to anchor phenylalanine to a polymeric support through its side chain is reported. To prove the usefulness of this strategy in solid-phase peptide synthesis, several bioactive peptides have been prepared including cyclic, C-modified, and protected peptides. The triazene linkage is formed by coupling the diazonium salt of Fmoc-Phe(pNH(2))-OAllyl to a MBHA-polystyrene resin previously functionalized with isonipecotic acid (90%). Further assembly of the peptide chain, cleavage from the resin using 2-5% TFA in DCM, and reduction of the resulting diazonium salt of the peptide with FeSO(4)·7H(2)O in DMF afforded the desired products in high purities (73-94%).

A novel method for the synthesis of para-substituted phenylalanine containing cyclic peptides is described. The main features of this strategy are the coupling of phenylalanine to the solid support through its side chain via a triazene linkage, on-resin cyclization of the peptide chain, cleavage of the cyclic peptide from the resin under mild acidic conditions and further transformation of the resulting diazonium salt. The usefulness of this approach is exemplified by the solid-phase synthesis of some derivatives of the naturally occurring cyclic depsipeptide zygosporamide.