Quinone-mediated hydrogen anode for non-aqueous reductive electrosynthesis.

Electrochemical synthesis can provide more sustainable routes to industrial chemicals. Electrosynthetic oxidations may often be performed 'reagent-free', generating hydrogen (H) derived from the substrate as the sole by-product at the counter electrode. Electrosynthetic reductions, however, require an external source of electrons.

Coupling-Condensation Strategy for the Convergent Synthesis of an Imidazole-Fused 2-Aminoquinoline NLRP3 Agonist.

The development of a convergent route to the NLRP3 (nucleotide-binding domain and leucine-rich repeat-containing protein 3) agonist BMS-986299 is reported. The synthesis relies on a key Miyaura borylation and a tandem Suzuki-Miyaura coupling between an iodoimidazole and an -aminochloroarene, followed by acid-mediated cyclization to afford the aminoquinoline core. The subsequent Boc cleavage and regioselective acylation afford the target compound.

Electrochemical Recycling of Adenosine Triphosphate in Biocatalytic Reaction Cascades.

Adenosine triphosphate (ATP) provides the driving force necessary for critical biological functions in all living organisms. In synthetic biocatalytic reactions, this cofactor is recycled using high-energy stoichiometric reagents, an approach that generates waste and poses challenges with enzyme stability. On the other hand, an electrochemical recycling system would use electrons as a convenient source of energy.

Cesium Amide-Catalyzed Selective Deuteration of Benzylic C-H Bonds with D and Application for Tritiation of Pharmaceuticals.

Hydrogen isotope exchange (HIE) represents one of the most attractive labeling methods to synthesize deuterium- and tritium-labeled compounds. Catalytic HIE methods that enable site-selective C-H bond activation and exchange labeling with gaseous isotopes D and T are of vital importance, in particular for high-specific-activity tritiation of pharmaceuticals. As part of our interest in exploring s-block metals for catalytic transformations, we found CsN(SiMe ) to be an efficient catalyst for selective HIE of benzylic C-H bonds with D gas.

Late-Stage Modification of Oligopeptides by Nickel-Catalyzed Stereoselective Radical Addition to Dehydroalanine.

Radical addition to dehydroalanine (Dha) represents an appealing, modular strategy to access non-canonical peptide analogues for drug discovery. Prior studies on radical addition to the Dha residue of peptides and proteins have demonstrated outstanding functional group compatibility, but the lack of stereoselectivity has limited the synthetic utility of this approach. Herein, we address this challenge by employing chiral nickel catalysts to control the stereoselectivity of radical addition to Dha on oligopeptides.

High Bulk-Density Amorphous Dispersions to Enable Direct Compression of Reduced Tablet Size Amorphous Dosage Units.

Amorphous solid dispersions (ASDs) are an attractive option to improve the bioavailability of poorly water-soluble compounds. However, the material attributes of ASDs can present formulation and processability challenges, which are often mitigated by the addition of excipients albeit at the expense of tablet size. In this work, an ASD manufacturing train combining co-precipitation and thin film evaporation (TFE) was used to generate high bulk-density co-precipitated amorphous dispersion (cPAD).

Efficient Aliphatic Hydrogen-Isotope Exchange with Tritium Gas through the Merger of Photoredox and Hydrogenation Catalysts.

Employment of a combination of an organophotoredox catalyst with Wilkinson's catalyst (Rh(PPh)Cl) has given rise to an unprecedented method for hydrogen-isotope exchange (HIE) of aliphatic C(sp)-H bonds of complex pharmaceuticals using T gas directly. Wilkinson's catalyst, commonly used for catalytic hydrogenations, was exploited as a precatalyst for activation of D or T and hydrogen atom transfer. In this combined methodology and mechanistic study, we demonstrate that by coupling photocatalysis with Rh catalysis, carbon-centered radicals generated via photoredox catalysis can be intercepted by Rh-hydride intermediates to deliver an effective hydrogen atom donor for hydrogen-isotope labeling of complex molecules in one step.

Electrochemically driven cross-electrophile coupling of alkyl halides.

Recent research in medicinal chemistry has suggested that there is a correlation between an increase in the fraction of sp carbons-those bonded to four other atoms-in drug candidates and their improved success rate in clinical trials. As such, the development of robust and selective methods for the construction of carbon(sp)-carbon(sp) bonds remains a critical problem in modern organic chemistry. Owing to the broad availability of alkyl halides, their direct cross-coupling-commonly known as cross-electrophile coupling-provides a promising route towards this objective.

Engineered Ribosyl-1-Kinase Enables Concise Synthesis of Molnupiravir, an Antiviral for COVID-19.

Molnupiravir (MK-4482) is an investigational antiviral agent that is under development for the treatment of COVID-19. Given the potential high demand and urgency for this compound, it was critical to develop a short and sustainable synthesis from simple raw materials that would minimize the time needed to manufacture and supply molnupiravir. The route reported here is enabled through the invention of a novel biocatalytic cascade featuring an engineered ribosyl-1-kinase and uridine phosphorylase.

Unlocking the Potential of High-Throughput Experimentation for Electrochemistry with a Standardized Microscale Reactor.

Organic electrochemistry has emerged as an enabling and sustainable technology in modern organic synthesis. Despite the recent renaissance of electrosynthesis, the broad adoption of electrochemistry in the synthetic community, and especially in industrial settings, has been hindered by the lack of general, standardized platforms for high-throughput experimentation (HTE). Herein, we disclose the design of the HT Chem, a high-throughput microscale electrochemical reactor that is compatible with existing HTE infrastructure and enables the rapid evaluation of a broad array of electrochemical reaction parameters.

Hierarchical Particle Approach for Co-Precipitated Amorphous Solid Dispersions for Use in Preclinical In Vivo Studies.

Amorphous solid dispersions (ASD) have become a well-established strategy to improve exposure for compounds with insufficient aqueous solubility. Of methods to generate ASDs, spray drying is a leading route due to its relative simplicity, availability of equipment, and commercial scale capacity. However, the broader industry adoption of spray drying has revealed potential limitations, including the inability to process compounds with low solubility in volatile solvents, inconsistent molecular uniformity of spray dried amorphous dispersions, variable physical properties across batches and scales, and challenges containing potent compounds.

Late-Stage Carbon Isotope Exchange of Aryl Nitriles through Ni-Catalyzed C-CN Bond Activation.

A facile one-pot strategy for CN and CN exchange with aryl, heteroaryl, and alkenyl nitriles using a Ni phosphine catalyst and BPh is described. This late-stage carbon isotope exchange (CIE) strategy employs labeled Zn(CN) to facilitate enrichment using the nonlabeled parent compound as the starting material, eliminating synthesis for precursor development. A broad substrate scope encompassing multiple pharmaceuticals is disclosed, including the preparation of [C] belzutifan to illustrate the exceptional functional group tolerance and utility of this labeling approach.

Biocatalytic oxidation of alcohols using galactose oxidase and a manganese(III) activator for the synthesis of islatravir.

Galactose oxidase (GOase) is a Cu-dependent metalloenzyme that catalyzes the oxidation of alcohols to aldehydes. An evolved GOase variant was recently shown to catalyze a desymmetrizing oxidation as the first enzymatic step in the biocatalytic synthesis of islatravir. Horseradish peroxidase (HRP) is required to activate the GOase, introducing cost and protein burden to the process.

Using nature's blueprint to expand catalysis with Earth-abundant metals.

Numerous redox transformations that are essential to life are catalyzed by metalloenzymes that feature Earth-abundant metals. In contrast, platinum-group metals have been the cornerstone of many industrial catalytic reactions for decades, providing high activity, thermal stability, and tolerance to chemical poisons. We assert that nature's blueprint provides the fundamental principles for vastly expanding the use of abundant metals in catalysis.

Late-Stage O Labeling of Primary Sulfonamides via a Degradation-Reconstruction Pathway.

A late-stage O labeling approach of sulfonamides that employs the corresponding unlabeled molecule as the starting material was developed. Upon deamination of the sulfonamide, a sulfinate intermediate was isotopically enriched using eco-friendly reagents H O and NH (aq) to afford a M+5 isotopologue of the parent compound. This degradation-reconstruction approach afforded isolated yields of up to 96 % for the stable isotope labeled (SIL) sulfonamides, and was compatible with multiple marketed therapeutics, including celecoxib, on a gram scale.

C-H Arylation in the Formation of a Complex Pyrrolopyridine, the Commercial Synthesis of the Potent JAK2 Inhibitor, BMS-911543.

The development of an improved short and efficient commercial synthesis of the JAK2 inhibitor, a complex pyrrolopyridine, BMS-911543, is described. During the discovery and development of this synthesis, a Pd-catalyzed C-H functionalization was invented which enabled the rapid union of the key pyrrole and imidazole fragments. The synthesis of this complex, nitrogen-rich heterocycle was accomplished in only six steps (longest linear sequence) from readily available materials.

Effects of Multiple Catalyst Deactivation Pathways and Continuous Ligand Recycling on the Kinetics of Pd-Catalyzed C-N Coupling Reactions.

Unusual Pd deactivation and inhibition pathways were observed in a C-N coupling system. Irreversible catalyst deactivation involved C-H insertion of Pd into BippyPhos leading to an off-cycle palladaphosphacyclobutene. Product inhibition led to deactivated Pd but released ligand in the process, allowing it to react with additional Pd precursor to re-enter the catalytic cycle.

Enantioselective Synthesis of a γ-Secretase Modulator via Vinylogous Dynamic Kinetic Resolution.

Two efficient asymmetric routes to γ-secretase modulator BMS-932481, under investigation for Alzheimer's disease, have been developed. The key step for the first route involves a challenging enantioselective hydrogenation of an unfunctionalized trisubstituted alkene to establish the benzylic stereocenter, representing a very rare case of achieving high selectivity on a complex substrate. The second route demonstrates the first example of a vinylogous dynamic kinetic resolution (VDKR) ketone reduction, where the carbonyl and the racemizable stereocenter are not contiguous, but are conjugated through a pyrimidine ring.

A Mild, Functional Group Tolerant Addition of Organozinc Nucleophiles to N-Activated Quinolines and Isoquinolines.

An addition of organozinc nucleophiles to N-acyl activated quinolines and isoquinolines is described. Simple transmetalation with the corresponding Grignard reagents using ZnCl forms organozinc compounds which are functional group tolerant and stable to reactive acyl chloride reagents for extended periods. A wide variety of substrates which include reactive electron-withdrawing groups are well tolerated to form 2-substituted dihydroquinolines and dihydroisoquinolines.

Synthesis of HIV-Maturation Inhibitor BMS-955176 from Betulin by an Enabling Oxidation Strategy.

A concise and scalable second generation synthesis of HIV maturation inhibitor BMS-955176 is described. The synthesis is framed by an oxidation strategy highlighted by a Cu mediated aerobic oxidation of betulin, a highly selective PIFA mediated dehydrogenation of an oxime, and a subsequent Lossen rearrangement which occurs through a unique reaction mechanism for the installation of the C17 amino functionality. The synthetic route proceeds in 7 steps with 47% overall yield and begins from the abundant and inexpensive natural product betulin.

Revisiting a Classic Transformation: A Lossen Rearrangement Initiated by Nitriles and "Pseudo-Catalytic" in Isocyanate.

The direct conversion of a hydroxamic acid to an amine has been accomplished in a single step in the synthesis of HIV drug candidate BMS-955176. This process utilizes catalytic base and proceeds under mild conditions (CHCN, cat. DBU, 60 °C), without the need for strong electrophiles required for typical Lossen rearrangements, and can be applied to aliphatic and aromatic hydroxamic acids.

Autoxidation Products of Betulonaldehyde.

Three major degradation products resulted from the exposure of betulonaldehyde (1) to air in solution at room temperature. From HRMS and NMR data, the products, which were isolated by preparative supercritical fluid chromatography (SFC), were identified as betulonic acid (2) and C-17 hydroperoxide epimers 3 (β-OOH) and 4 (α-OOH). For 3 and 4, the H-18 multiplet pattern of the isolated products established the configuration at C-17.

Unusual pyrimidine participation: efficient stereoselective synthesis of potent dual orexin receptor antagonist MK-6096.

An asymmetric synthesis of dual orexin receptor antagonist MK-6096 (1) is described. Key steps for the trans-2,5-disubstituted piperidinyl ether fragment include a biocatalytic transamination, a trans-selective Mukaiyama aldol, and a regioselective pyridyl SNAr process. The pyrimidyl benzoic acid was synthesized via a Negishi coupling and a nitrile hydrolysis.

Reaction development and mechanistic study of a ruthenium catalyzed intramolecular asymmetric reductive amination en route to the dual Orexin inhibitor Suvorexant (MK-4305).

The first example of an intramolecular asymmetric reductive amination of a dialkyl ketone with an aliphatic amine has been developed for the synthesis of Suvorexant (MK-4305), a potent dual Orexin antagonist under development for the treatment of sleep disorders. This challenging transformation is mediated by a novel Ru-based transfer hydrogenation catalyst that provides the desired diazepane ring in 97% yield and 94.5% ee.