DNA-Encoded Macrocyclic Peptide Libraries Enable the Discovery of a Neutral MDM2-p53 Inhibitor.

Synthetic macrocyclic peptides are an emerging molecular class for both targeting intracellular protein-protein interactions (PPIs) and providing an oral modality for drug targets typically addressed by biologics. Display technologies, such as mRNA and phage display, often yield peptides that are too large and too polar to achieve passive permeability or oral bioavailability without substantial off-platform medicinal chemistry. Herein, we use DNA-encoded cyclic peptide libraries to discover a neutral nonapeptide, UNP-6457, that inhibits MDM2-p53 interaction with an IC of 8.

Stretching Peptides to Generate Small Molecule β-Strand Mimics.

Advances in the modulation of protein-protein interactions (PPIs) enable both characterization of PPI networks that govern diseases and design of therapeutics and probes. The shallow protein surfaces that dominate PPIs are challenging to target using standard methods, and approaches for accessing extended backbone structures are limited. Here, we incorporate a rigid, linear, diyne brace between side chains at the to 2 positions to generate a family of low-molecular-weight, extended-backbone peptide macrocycles.

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.

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.

Rigid Peptide Macrocycles from On-Resin Glaser Stapling.

Peptide macrocycles are widely utilized in the development of high affinity ligands, including stapled α-helices. The linear rigidity of a 1,3-diynyl linkage provides an optimal distance (7 Å) between β-carbons of the i,i+4 amino acid side chains, thus suggesting its utility in stabilizing α-helical structures. Here, we report the development of an on-resin strategy for an intramolecular Glaser reaction between two alkyne-terminated side chains by using copper chloride, an essential bpy-diol ligand, and diisopropylethylamine at room temperature.

Adapting the Glaser Reaction for Bioconjugation: Robust Access to Structurally Simple, Rigid Linkers.

Copper-mediated coupling between alkynes to generate a structurally rigid, linear 1,3-diyne linkage has been known for over a century. However, the mechanistic requirement to simultaneously maintain Cu and an oxidant has limited its practical utility, especially for complex functional molecules in aqueous solution. We find that addition of a specific bpy-diol ligand protects unprotected peptides from Cu -mediated oxidative damage through the formation of an insoluble Cu gel which solves the critical challenge of applying Glaser coupling to substrates that are degraded by Cu .

Base-catalyzed diastereoselective trimerization of trifluoroacetone.

Amphiphilic fluorocarbons have unique properties that facilitate their self assembly and adhesion to both inorganic and biological substrates. Incorporation of these moieties into valuable constructs typically require complex synthetic routes that have limited their use. Here, the base-catalyzed diastereoselective synthesis of 6-methyl-2,4,6-tris(trifluoromethyl)tetrahydro-2H-pyran-2,4-diol is reported.

Rhodium(II)-catalyzed nondirected oxidative alkenylation of arenes: arene loading at one equivalent.

A bimetallic Rh(II) catalyst promoted the C-H alkenylation of simple arenes at 1.0 equivalent without the use of a directing group. A phosphine ligand as well as cooperative reoxidation of Rh(II) with Cu(TFA)2 and V2O5 proved essential in providing monoalkenylated products in good yields and selectivities, especially with di- and trisubstituted arenes.

Mechanistic investigation of the enantioselective intramolecular stetter reaction: proton transfer is the first irreversible step.

A study on the mechanism of the asymmetric intramolecular Stetter reaction is reported. This investigation includes the determination of the rate law, kinetic isotope effects, and competition experiments. The reaction was found to be first order in aldehyde and azolium catalyst or free carbene.

Stability of MCT/LCT-based total nutrient admixtures for neonatal use over 30 hours at room temperature: applying pharmacopeial standards.

Background: United States Pharmacopeial Chapter <729> places a limit on the percentage of large fat globules >5 microm, expressed as a PFAT5 of <0.05% for all native lipid emulsions. Some adult total nutrient admixtures (TNAs) have also remained below this limit for up to 48 hours.

Calcium and phosphate compatibility in low-osmolarity parenteral nutrition admixtures intended for peripheral vein administration.

Background: Precipitation of calcium (Ca) and phosphate (P) salts can lead to potentially lethal outcomes, especially in low-osmolarity parenteral nutrition (LO-PN) formulations. Three concentrations of amino acids (AA) and 2 concentrations of calcium gluconate and sodium phosphate injections on the compatibility of Ca and P in LO-PN admixtures were studied.

Methods: Final AA concentrations of 1%, 2%, or 3% (n = 3) and 5% glucose (G) were prepared with either 2.

Physical compatibility of neonatal total parenteral nutrition admixtures containing organic calcium and inorganic phosphate salts in a simulated infusion at 37 degrees C.

Objective: Within an incubator environment at 37 degrees C, we evaluated the physical compatibility of calcium (Ca) and phosphate (P) in simulated neonatal total parenteral nutrition (TPN) infusions.

Design: Representative neonatal TPN formulas containing four concentrations of amino acids [AA] (1-4 g/dL) and two levels of dextrose [D] (5 and 10 g/dL) were monitored for calcium-phosphate precipitate formation over 24 hours using a laser-based particle counting technique.

Setting: Research Laboratory.

Stability of total nutrient admixtures with lipid injectable emulsions in glass versus plastic packaging.

Purpose: The physical stability of two emulsions compounded as part of a total nutrient admixture (TNA) was studied in lipids packaged in either glass or plastic containers.

Methods: Five weight-based adult TNA formulations that were designed to meet the full nutritional needs of adults with body weights between 40 and 80 kg were studied. Triplicate preparations of each TNA were assessed over 30 hours at room temperature by applying currently proposed United States Pharmacopeia (USP) criteria for mean droplet diameter, large-diameter tail, and globule-size distribution (GSD) for lipid injectable emulsions.

Establishing a stability window for medium- and long-chain-triglyceride lipid-based total nutrient admixtures using USP standards.

Purpose: The stability window of medium-chain triglyceride (MCT) and long-chain-triglyceride (LCT) lipid-based total nutrient admixtures (TNAs) was studied.

Methods: Sixteen different admixtures were selected for study. Of these, eight base macronutrient concentrations representing low and high concentrations were selected, along with low and high concentrations of electrolytes.

Physicochemical stability of highly concentrated total nutrient admixtures for fluid-restricted patients.

Purpose: The physicochemical stability of highly concentrated total nutrient admixtures (TNAs) for fluid-restricted patients was studied.

Methods: Five TNAs made from lipid injectable emulsions (50:50 mixture of medium-chain and long-chain triglycerides) designed to meet the full nutritional needs of adults with body weights of 40-80 kg were chosen. Protein was included in the TNAs at 1.