Electrochemical γ-Selective Deuteration of Pyridines.

Herein, we first report a γ-selective deuteration reaction of pyridines via H/D exchange without the need for preinstalled directing groups and transformable functional groups. The electrochemical process offers an attractive approach to producing γ-deuterated pyridines under gentle conditions. The broad substrate scope, excellent deuterium incorporation, and remarkable selectivity of the electrochemical method make it applicable for the late-stage modification of pharmaceutical molecules.

Modular Approach to Highly Substituted 3-Methylpyridones.

A method has been developed for the rapid synthesis of highly substituted 3-methylpyridones via the condensation of Baylis-Hillman amines and ketones under benzoic acid catalysis. The process features readily available starting materials, broad substrate scope, high functional group tolerance, excellent regioselectivity, and gram-scale synthesis. We envision that this on-demand construction of 3-methylpyridones will provide exciting opportunities in biological research, therapeutics, and material sciences.

Design, synthesis, and pharmacological evaluation of quinazoline derivatives as novel and potent pan-JAK inhibitors.

Janus kinases (JAKs) play a critical role in modulating the function and expression of inflammatory cytokines related to rheumatoid arthritis (RA). Herein, we report the design, synthesis, and structure-activity relationships (SARs) of a series of novel quinazoline derivatives as JAK inhibitors. Among these inhibitors, compound 11n showed high potency against JAKs (JAK1/JAK2/JAK3/TYK2, IC50 = 0.40, 0.83, 2.10, 1.95 nM), desirable metabolic characters, and excellent pharmacokinetic properties. In collagen-induced arthritis (CIA) models, compound 11n exhibited significant reduction in joint swelling with good safety, which could be served as a potential therapeutic candidate for the treatment of inflammatory diseases.

A Microfluidic Device for Tobacco Ringspot Virus Detection by Electrochemical Impedance Spectroscopy.

Aiming at the problem of how to achieve the rapid detection of pathogenic microorganisms, this paper takes tobacco ringspot virus as the detection object, designs the impedance detection and analysis platform of tobacco ringspot virus based on microfluidic impedance method, establishes an equivalent circuit model to analyze the experimental results, and determines the optimal detection frequency of tobacco ringspot virus detection. Based on this frequency, an impedance-concentration regression model was established for the detection of tobacco ringspot virus in a tobacco ringspot virus detection device. Based on this model, a tobacco ringspot virus detection device was designed by using an AD5933 impedance detection chip. A comprehensive test study was carried out on the developed tobacco ringspot virus detection device through various testing methods, which verified the feasibility of the tobacco ringspot virus detection device and provided technical support for the field detection of pathogenic microorganisms.

Catalyst-Free α-Allylation of Dihydroisoquinolines with Morita-Baylis-Hillman Carbonates and Its Applications in the Construction of Benzo[a]quinolizidines.

In this work, a mild and efficient catalyst-free α-allylation of 3,4-dihydroisoquinoline imines with Morita-Baylis-Hillman (MBH) carbonates was reported. The scopes of 3,4-dihydroisoquinolines and MBH carbonates as well as gram-scale synthesis were investigated, and densely functionalized adducts were obtained in moderate to good yields. The synthetic utility of these versatile synthons was further demonstrated by the facile synthesis of diverse benzo[a]quinolizidine skeletons.

Electrooxidative Dearomatization of Inactive Biphenyls to Cyclohexadienones.

An efficient electrooxidative dearomatization of inactive biphenyls has been developed under mild and easy-to-operate conditions. The protocol provides a powerful tool for the rapid synthesis of cyclohexadienones in moderate to high yields with wide substrate scope and good functional group compatibility even to oxidation-sensitive motifs. This method provides an environment-friendly and direct approach for the construction of C-O bonds with high regioselectivity.

Catalyst-Controlled Regiodivergent Synthesis of α/ß-Dipeptide Derivatives via N-Allylic Alkylation of O-Alkyl Hydroxamates with MBH Carbonates.

A controllable and regiodivergent N-allylation reaction involving readily available O-alkyl hydroxamates derived from natural α-amino acids has been developed, allowing regiospecific access to α/ß-dipeptides containing α-unsaturated ß-amino acids moieties in moderate to good yields. The regioselectivity could be conveniently switched by alternation of the catalysts and solvents.

Direct C(sp3)-H allylation of 2-alkylpyridines with Morita-Baylis-Hillman carbonates via a tandem nucleophilic substitution/aza-Cope rearrangement.

A base- and catalyst-free C(sp3)-H allylic alkylation of 2-alkylpyridines with Morita-Baylis-Hillman (MBH) carbonates is described. A plausible mechanism of the reaction might involve a tandem SN2' type nucleophilic substitution followed by an aza-Cope rearrangement. Various alkyl substituents on 2-alkylpyridines were tolerated in the reaction to give the allylation products in 26-91% yields. The developed method provides a straightforward and operational simple strategy for the allylic functionalization of 2-alkypyridine derivatives.

Modular and Stereoselective Approach to Highly Substituted Indole/Pyrrole-Fused Diazepanones.

A one-pot synthetic method for indole/pyrrole-fused 1,4-diazepanone scaffolds has been developed. This method involves a sequential amide coupling/intramolecular aza-Michael addition of 1H-indole/pyrrole-2-carboxylic acids with Morita-Baylis-Hillman-derived allylamines. The readily available starting materials, good stereoselectivity, and gram-scale synthesis make this method valuable for the construction of highly substituted fused heterocycles containing the 1,4-diazepanone moiety.

Tyrosine-Reactive Cross-Linker for Probing Protein Three-Dimensional Structures.

Cross-linking mass spectrometry (XL-MS) has made significant progress in understanding the structure of protein and elucidating architectures of larger protein complexes. Current XL-MS applications are limited to targeting lysine, glutamic acid, aspartic acid, and cysteine residues. There remains a need for the development of novel cross-linkers enabling selective targeting of other amino acid residues in proteins. Here, a novel simple cross-linker, namely, [4,4'-(disulfanediylbis(ethane-2,1-diyl)) bis(1,2,4-triazolidine-3,5-dione)] (DBB), has been designed, synthesized, and characterized. This cross-linker can react selectively with tyrosine residues in protein through the electrochemical click reaction. The DBB cross-links produced the characteristic peptides before and after electrochemical reduction, thus permitting the simplified data analysis and accurate identification for the cross-linked products. This is the first time a cross-linker is developed for targeting tyrosine residues on protein without using photoirradiation or a metal catalyst. This strategy might potentially be used as a complementary tool for XL-MS to probe protein 3D structures, protein complexes, and protein-protein interaction.

Electroselective and Controlled Reduction of Cyclic Imides to Hydroxylactams and Lactams.

An efficient and practical electrochemical method for selective reduction of cyclic imides has been developed using a simple undivided cell with carbon electrodes at room temperature. The reaction provides a useful strategy for the rapid synthesis of hydroxylactams and lactams in a controllable manner, which is tuned by electric current and reaction time, and exhibits broad substrate scope and high functional group tolerance even to reduction-sensitive moieties. Initial mechanistic studies suggest that the approach heavily relies on the utilization of amines (e.g., i-Pr2NH), which are able to generate α-aminoalkyl radicals. This protocol provides an efficient route for the cleavage of C-O bonds under mild conditions with high chemoselectivity.

An acidic residue reactive and disulfide bond-containing cleavable cross-linker for probing protein 3D structures based on electrochemical mass spectrometry.

Cross-linking mass spectrometry (XL-MS) has attracted broad attention because of the capability to probe three-dimensional structure of proteins. Up to now, several amine-reactive cross-linkers have been developed for characterization of proteins and protein complexes. However, spatial information retrieved by XL-MS is still limited, partly because the strategies using an acidic residue reactive cross-linker have been rarely reported. In this paper, an acidic residue (e.g. aspartic acid, glutamic acid)-specific, disulfide bond-containing, cleavable cross-linker with a length of 13.1 Å, named 3,3'-dithiobis(propanoic dihydrazide), was presented for the first time. In addition, a novel approach using the cross-linker was proposed for unambiguous characterization of peptides and proteins with disulfide bonds. After cross-linked, the peptides could be electrochemically reduced, then characterized by high performance liquid chromatography mass spectrometry. For demonstration, the approach has been adopted to characterize the emideltide, insulin, and myoglobin, of which four pairs of intrachain cross-links have been successfully identified in myoglobin. The results showed that the cross-links displayed predictable fragmentation pattern upon collision induced dissociation (CID), thus admitting simplifying data analysis. In summary, this work introduces a novel type of cross-linker utilized for cross-linking and a new strategy to XL-MS technology for comprehensively understanding the three-dimensional structure of proteins.

Disulfide linkage assignment based on reducing electrochemistry and mass spectrometry using a lead electrode.

The study of disulfide linkage is a crucial part of the quality assessment of biopharmaceutical products because disulfide bonds stabilize the tertiary structure of proteins and maintain protein functions. Therefore, a suitable method is highly required for disulfide linkage assignment when nested disulfide bonds formed with closely spaced cysteine residues. A novel approach for disulfide linkage assignment of disulfide-rich peptides and proteins via electrochemical reduction on a lead electrode with mass spectrometry is presented in this paper. The method features partial electrochemical reduction and alkylation of peptides followed by alkylated peptide sequencing based on tandem mass spectrometry. Lead was chosen for the first time as an electrode material for disulfide bond reduction, because it has the advantages of maintenance free (only infrequent polishing needed), easy operation in DC mode, and reusability. Without any special sample preparation and any chemical reduction agents, disulfide bond in peptides can be cleaved rapidly. The new method was successfully tested with two peptides and one protein containing nested disulfide bonds.

Sulfonamide-Trapping Reactions of Thermally Generated Benzynes.

Reactions of tethered, tertiary sulfonamides with thermally generated benzynes are reported. Typically, the N-S bonds in the substrates cleave, and saturated heterocycles [tetrahydroquinolines ( n = 2) and indolines ( n = 1)] are formed. The process is accompanied by either sulfonyl transfer or desulfonylation from a zwitterionic intermediate, with the favored pathway being largely dependent upon the size (5- vs 6-membered) of the N-containing ring in the zwitterion.

A cascade of acid-promoted C-O bond cleavage and redox reactions: from oxa-bridged benzazepines to benzazepinones.

A sequence of C-O bond cleavage and redox reactions in oxa-bridged azepines was realized under acid promoted conditions. This protocol provides an atom-economical and straightforward approach to access benzo[b]azepin-5(2H)-ones in high yields. The formal synthesis of tolvaptan was achieved by exploiting this new transformation.

Structure-functional selectivity relationship studies of ß-arrestin-biased dopamine D2 receptor agonists.

Functionally selective G protein-coupled receptor (GPCR) ligands, which differentially modulate canonical and noncanonical signaling, are extremely useful for elucidating key signal transduction pathways essential for both the therapeutic actions and side effects of drugs. However, few such ligands have been created, and very little purposeful attention has been devoted to studying what we term: "structure-functional selectivity relationships" (SFSR). We recently disclosed the first ß-arrestin-biased dopamine D(2) receptor (D(2)R) agonists UNC9975 (44) and UNC9994 (36), which have robust in vivo antipsychotic drug-like activities. Here we report the first comprehensive SFSR studies focused on exploring four regions of the aripiprazole scaffold, which resulted in the discovery of these ß-arrestin-biased D(2)R agonists. These studies provide a successful proof-of-concept for how functionally selective ligands can be discovered.

Synthesis of hexahydrobenzo[b]pyrimido[4,5-h][1,6]naphthyridines via an intramolecular hetero-Diels-Alder reaction.

Method development was completed for a strategy to access a novel pyrimidine-fused heterocyclic scaffold. The key step for this synthetic route entails an intramolecular inverse electron demand hetero-Diels-Alder reaction of imines or iminiums formed in situ from allylaminopyrimidinealdehydes 3 and anilines. The reactions provided exclusively cis-configuration products 6. Products 6 were readily precipitated in the reaction solution in good to excellent yields. Further transformations of the phenylthio group were demonstrated by an oxidation and subsequent nucleophilic substitution sequence. The synthetic strategy provides an efficient way to access libraries of the tetracyclic pyrimidine-fused heterocycles that can be explored for potential pharmaceutical or biological activities.

A cascade reaction with iminium ion isomerization as the key step leading to tetrahydropyrimido[4,5-d]pyrimidines.

A novel cascade reaction of aminopyrimidines 1 with N-alkyl amino acids or analogues was investigated. The keys to this cascade are the isomerization of an iminium ion formed between the aldehyde group in pyrimidine and the secondary amine of an amino acid, and subsequent cyclization to the neighboring amino group. This sequence could be useful in the synthesis of novel tetrahydropyrimido[4,5-d]pyrimidine libraries.

Synthesis of novel pyrimidine fused 8-membered heterocycles via iminium ion cyclization reactions.

Novel tricyclic pyrimidine-fused 8-membered heterocycles were prepared by an iminium ion cyclization using pyrimidinediamine systems with electron-rich aromatic rings.