A Shelf Stable Fmoc Hydrazine Resin for the Synthesis of Peptide Hydrazides.

C-terminal hydrazides are an important class of synthetic peptides with an ever expanding scope of applications, but their widespread application for chemical protein synthesis has been hampered due to the lack of stable resin linkers for synthesis of longer and more challenging peptide hydrazide fragments. We present a practical method for the regeneration, loading, and storage of trityl-chloride resins for the production of hydrazide containing peptides, leveraging 9-fluorenylmethyl carbazate. We show that these resins are extremely stable under several common resin storage conditions. The application of these resins to solid phase peptide synthesis (SPPS) is demonstrated through the synthesis of the 40-mer GLP-1R agonist peptide "P5". These studies support the broad utility of Fmoc-NHNH-Trt resins for SPPS of C-terminal hydrazide peptides.

Native Chemical Ligation of Peptides and Proteins.

For over 20 years, native chemical ligation (NCL) has played a pivotal role in enabling total synthesis and semisynthesis of increasingly complex peptide and protein targets. Classical NCL proceeds by chemoselective reaction of two unprotected polypeptide chains in near-neutral-pH, aqueous solution and is made possible by the presence of a thioester moiety on the C-terminus of the N-terminal peptide fragment and a natural cysteine residue on the N-terminus of the C-terminal peptide fragment. The reaction yields an amide bond adjacent to cysteine at the ligation site, furnishing a native protein backbone in a traceless manner. This unit highlights a number of recent and powerful advances in the methodology and outlines their particular uses, facilitating application in the synthesis of challenging protein targets. © 2019 by John Wiley & Sons, Inc.

Leveraging the Knorr Pyrazole Synthesis for the Facile Generation of Thioester Surrogates for use in Native Chemical Ligation.

Facile synthesis of C-terminal thioesters is integral to native chemical ligation (NCL) strategies for chemical protein synthesis. We introduce a new method of mild peptide activation, which leverages solid-phase peptide synthesis (SPPS) on an established resin linker and classical heterocyclic chemistry to convert C-terminal peptide hydrazides into their corresponding thioesters via an acyl pyrazole intermediate. Peptide hydrazides, synthesized on established trityl chloride resins, can be activated in solution with stoichiometric acetyl acetone (acac), readily proceed to the peptide acyl pyrazoles. Acyl pyrazoles are mild acylating agents and are efficiently exchanged with an aryl thiol, which can then be directly utilized in NCL. The mild, chemoselective, and stoichiometric activating conditions allow this method to be utilized through multiple sequential ligations without intermediate purification steps.

Expedient on-resin synthesis of peptidic benzimidazoles.

The benzimidazole moiety is a ubiquitous pharmacophore present in numerous anthelmintic, antibacterial, antiviral, antineoplastic, and antifungal drugs. While the polypharmacology of this heterocycle has spurred the development of numerous solution-phase syntheses, only a handful of disparate and inefficient methods detailing its synthesis on-resin have been reported. Here we report the concise and expedient syntheses of internal and C-terminal peptidic benzimidazoles - an emerging class of peptide deformylase (PDF)-inhibiting antimicrobials. This method benefits from being performed wholly on solid-phase at room temperature resulting in minimal purification and tolerance of temperature-sensitive functionality.

Analysis of Loops that Mediate Protein-Protein Interactions and Translation into Submicromolar Inhibitors.

Effective strategies for mimicking α-helix and ß-strand epitopes have been developed, producing valuable inhibitors for some classes of protein-protein interactions (PPIs). However, there are no general strategies for translating loop epitopes into useful PPI inhibitors. In this work, we use the LoopFinder program to identify diverse sets of "hot loops," which are loop epitopes that mediate PPIs. These include loops that are well-suited to mimicry with macrocyclic compounds, and loops that are most similar to variable loops on antibodies and ankyrin repeat proteins. We present data-driven criteria for scoring loop-mediated PPIs, uncovering a trove of potentially druggable interactions. We also use unbiased clustering to identify common structures among the hot loops. To translate these insights into real-world inhibitors, we describe a robust, diversity-oriented strategy for the rapid production and evaluation of cyclized loops. This method is applied to a computationally identified loop in the PPI between stonin2 and Eps15, producing submicromolar inhibitors. The most potent inhibitor is well-structured in water and successfully mimics the native epitope. Overall, these computational and experimental strategies provide new opportunities to design inhibitors for an otherwise intractable set of PPIs.

Potential for community programs to prevent depression in older people.

Depression is one of the most common mental health disorders in older people. Sequelae include unnecessary suffering, excess physical and social disability, exacerbation of co-existing illness, earlier death, and overuse of services. There are currently no reported public health approaches to prevent late-life depression. Five risk factors appear susceptible to community-level prevention programs: recurrent depression, commonly undertreated precipitants, vascular disease, functional impairments, and metabolite abnormalities. We propose three broad but interacting prevention methods: increasing literacy about late-life depression, exercise, and dietary supplements.