Synthesis of paenipeptin C' analogues employing solution-phase CLipPA chemistry

Harnessing the power of a photoinitiated thiol-ene "click" reaction for the efficient synthesis of S-lipidated collagen model peptide amphiphiles

A photoinitiated thiol-ene "click" reaction was used to synthesize S-lipidated collagen model peptide amphiphiles. Use of 2-iminothiolane provided an epimerization-free thiol handle required for thiol-ene based incorporation of lipid moieties onto collagen-based peptide sequences. This approach not only led to improvements in the triple helical characteristics of the resulting collagen model peptides but also increased the aqueous solubility of the peptide amphiphiles. As a result, this methodology holds significant potential for the design and advancement of functional peptide amphiphiles, offering enhanced capabilities across a wide range of applications.

Synthesis and characterization of mono S-lipidated peptide hydrogels: a platform for the preparation of reactive oxygen species responsive materials

In this work we report the synthesis of mono lipidated peptides containing a 3-mercaptopropionate linker in the N-terminus by means of a photoinitiated thiol-ene reaction (S-lipidation). We evaluate the self-assembling and hydrogelation properties of a library of mono S-lipidated peptides containing lipid chains of various lengths and demonstrate that hydrogelation was driven by a balance between the lipid chain's hydrophobicity and the peptide's facial hydrophobicity. We further postulate that a simple calculation using estimated values of log D could be used as a predictor of hydrogelation when designing similar systems. A mono S-lipidated peptide containing a short lipid chain that formed hydrogels was fully characterized and a mechanism for the peptide hydrogelation developed. Finally, we demonstrate that the presence of the thioether group in the mono S-lipidated peptide hydrogels, which is a feature lacking in conventional N-acyl lipidated systems, enables the controlled disassembly of the gel via oxidation to the sulfoxide by reactive oxygen species in accordance with a hydrophobicity-modulated strategy. Thus, we conclude that mono S-lipidated peptide hydrogels constitute a novel and simple tool for the development of tissue engineering and targeted drug delivery applications of diseases with overexpression of reactive oxygen species (e.g. degenerative and metabolic diseases, and cancers).

Discovery, Synthesis, and Optimization of Peptide-Based Antibiotics

The rise of multidrug resistant bacteria has significantly compromised our supply of antibiotics and poses an alarming medical and economic threat to society. To combat this problem, it is imperative that new antibiotics and treatment modalities be developed, especially those toward which bacteria are less capable of developing resistance. Peptide natural products stand as promising candidates to meet this need as bacterial resistance is typically slow in response to their unique modes of action. They also have additional benefits including favorable modulation of host immune responses and often possess broad-spectrum activity against notoriously treatment resistant bacterial biofilms. Moreover, nature has provided a wealth of peptide-based natural products from a range of sources, including bacteria and fungi, which can be hijacked in order to combat more dangerous clinically relevant infections.This Account highlights recent advances in the total synthesis and development of a range of peptide-based natural product antibiotics and details the medicinal chemistry approaches used to optimize their activity.In the context of antibiotics with potential to treat Gram-positive bacterial infections, this Account covers the synthesis and optimization of the natural products daptomycin, glycocin F, and alamethicin. In particular, the reported synthesis of daptomycin highlights the utility of on-resin ozonolysis for accessing a key kynurenine residue from the canonical amino acid tryptophan. Furthermore, the investigation into glycocin F analogues uncovered a potent lead compound against Lactobacillus plantarum that bears a non-native thioacetal linkage to a N-acetyl-d-glucosamine (GlcNAc) sugar, which is otherwise O-linked in its native form.For mycobacterial infections, this Account covers the synthesis and optimization of teixobactin, callyaerin A, lassomycin, and trichoderin A. The synthesis of callyaerin A, in particular, highlighted the importance of a (Z)-2,3-diaminoacrylamide motif for antimicrobial activity against Mycobacterium tuberculosis, while the synthesis of trichoderin A highlighted the importance of (R)-stereoconfiguration in a key 2-amino-6-hydroxy-4-methyl-8-oxodecanoic acid (AHMOD) residue.Lastly, this Account covers lipopeptide antibiotics bearing activity toward Gram-negative bacterial infections, namely, battacin and paenipeptin C. In both cases, optimization of the N-terminal lipid tails led to the identification of analogues with potent activity toward Escherichia coli and Pseudomonas aeruginosa.

Thiol-ene enabled preparation of S-lipidated anti-HBV peptides

Despite significant efforts made towards treatments for Hepatitis B virus (HBV), a long-term curative treatment has thus far eluded scientists. Recently, the Sodium Taurocholate Co-Transporting Polypeptide (NTCP) receptor has been identified as the entry pathway of HBV into hepatocytes. Myrcludex B, an N-terminally myristoylated 47-mer peptide mimic of the preS1 domain of the Hepatitis B virion, was identified as a potent protein-protein interaction (PPI) inhibitor blocking HBV fusion (IC50 = 140 pM). Herein we report an optimised chemical synthesis of Myrcludex B and a series of novel analogues. Employing a small modification to the Cysteine Lipidation of a Peptide or Amino acid (CLipPA) thiol-ene reaction, a library of S-lipidated Myrcludex B and truncated (21-mer) analogues were prepared, providing novel chemical space to probe for the discovery of novel anti-HBV peptides. The S-lipidated analogues showed an equivalent or a slight decrease (∼2-fold) in binding effectiveness to NTCP expressing hepatocytes compared to Myrcludex B. Three S-lipidated analogues were highly potent HBV inhibitors (IC50 0.97-3.32 nM). These results demonstrate that incorporation of heteroatoms into the lipid 'anchor' is tolerated by this antiviral scaffold and to the best of our knowledge constitutes the first report of potent S-lipidated antiviral peptides. Interestingly, despite only moderate reductions in binding effectiveness, truncated analogues possessed dramatically reduced inhibitory activity thus providing new insights into the structure activity relationship of these hitherto unreported antiviral S-lipopeptides.

Photo-induced radical thiol-ene chemistry: a versatile toolbox for peptide-based drug design

While the global market for peptide/protein-based therapeutics is witnessing significant growth, the development of peptide drugs remains challenging due to their low oral bioavailability, poor membrane permeability, and reduced metabolic stability. However, a toolbox of chemical approaches has been explored for peptide modification to overcome these obstacles. In recent years, there has been a revival of interest in photoinduced radical thiol-ene chemistry as a powerful tool for the construction of therapeutic peptides.

Synthesis of Lipopeptides by CLipPA Chemistry

Lipidation of polypeptides with a fatty acid to form N-linked lipopeptides can be a time consuming process due to the need to mask other reactive function groups present on the side chains of amino acids. Cysteine Lipidation on a Peptide or Amino acid (CLipPA) technology enables the direct lipidation of unprotected peptides containing a free thiol group to afford S-lipidated lipopeptides. A generalized procedure for the synthesis of S-lipopeptides is described which facilities rapid preparation of tens of analogs of lipopeptides from a single thiolated polypeptide precursor.

Applications of Thiol-Ene Chemistry for Peptide Science

Radical thiol-ene chemistry has been demonstrated for a range of applications in peptide science, including macrocyclization, glycosylation and lipidation amongst a myriad of others. The thiol-ene reaction offers a number of advantages in this area, primarily those characteristic of "click" reactions. This provides a chemical approach to peptide modification that is compatible with aqueous conditions with high orthogonality and functional group tolerance. Additionally, the use of a chemical approach for peptide modification affords homogeneous peptides, compared to heterogeneous mixtures often obtained through biological methods. In addition to peptide modification, thiol-ene chemistry has been applied in novel approaches to biological studies through synthesis of mimetics and use in development of probes. This review will cover the range of applications of the radical-mediated thiol-ene reaction in peptide and protein science.