Convenient route to Fmoc-homotyrosine via metallaphotoredox catalysis and its use in the total synthesis of anabaenopeptin cyclic peptides

Herein, we report the first solid-phase total synthesis of the natural cyclic peptide anabaenopeptin F and the use of metallaphotoredox catalysis to overcome the key challenges associated with the preparation of the non-proteinogenic amino acid homotyrosine contained in these peptides. Starting from L-homoserine, enantiopure Fmoc-protected homotyrosine was prepared in a straightforward manner by metallaphotoredox catalysis with N-Fmoc-(S)-2-amino-4-bromobutanoic acid and 4-tert-butoxybromobenzene partners. The prepared protected amino acid was used in solid-phase peptide synthesis to achieve the total synthesis of anabaenopeptin F and establish the stereochemistry of the isoleucine residue. Protease inhibition studies with the synthesized anabaenopeptin F showed inhibitory activities against carboxypeptidase B in the low nanomolar range. The high convergency of the synthetic methodologies paves the way for the rapid access to N-Fmoc-protected non-proteinogenic and unnatural amino acids and the total synthesis of complex bioactive peptides containing these amino acids.

Head-to-tail cyclization for the synthesis of naturally occurring cyclic peptides on organophosphorus small-molecular supports

4,4′-bis(diphenylphosphinyloxyl) diphenyl ketoxime and 4-diphenyl phospholoxy benzyl alcohol were designed and prepared as supports for peptide synthesis. The total synthesis of cyclic peptides in a resin-free manner was successfully demonstrated.

A flow-based transition-metal-catalysed hydrogenolysis strategy to facilitate peptide side-chain deprotection

Orthogonal deprotection methodologies are an invaluable tool for the construction of site-specially modified peptides. Here, we report a facile 10% Pd/CaCO₃-based procedure to selectively mediate Nβ-side-chain Cbz-lysis from extended peptide sequences in the presence of trityl and t-Butyl protecting groups.

Total Synthesis and Antimalarial Activity of Dominicin, a Cyclic Octapeptide from a Marine Sponge

Dominicin, a macrocyclic peptide isolated from the marine sponge Eurypon laughlini, has been synthesized for the first time by solid-phase peptide synthesis. The strategy uses oxime resin and takes advantage of the nucleophile susceptibility of the oxime ester bond. The synthesis relies on the preparation of a linear precursor followed by on-resin head-to-tail concomitant cyclization-cleavage. This is the first report of the use of a Boc/O^tBu biorthogonal protection strategy on oxime resin to facilitate concomitant N-terminal and side-chain tert-butyl ether deprotection cyclization of unprotected peptides. Also, we report the first antimalarial investigation of dominicin. Interestingly, the natural macrocyclic peptide demonstrates effective low micromolar activity (1.8 μM) against the chloroquine-mefloquine-pyrimethamine-resistant Dd2 strain of Plasmodium falciparum.

Total synthesis and antimalarial activity of mortiamides A–D

This work describes the first total synthesis of mortiamides and their anti-malarial activity against a multi-drug resistant strain of Plasmodium falciparum.

Synthesis of C-terminal glycopeptidesviaoxime resin aminolysis

We developed a general solid-phase approach to complex C-terminal glycopeptides.