Enantiospecific Total Synthesis of (+)-Tanikolide via a Key [2,3]-Meisenheimer Rearrangement with an Allylic Amine N-Oxide-Directed Epoxidation and a One-Pot Trichloroisocyanuric Acid N-Debenzylation and N-Chlorination

Asymmetric Carbene Transfer: Enhancing Chemical Diversity for Drug Discovery

The quest to explore chemical space is vital for identifying novel disease targets, impacting both the effectiveness and safety profile of therapeutic agents. The tangible chemical space, currently estimated at a conservative 108 synthesized compounds, pales in comparison to the theoretically conceivable diversity of 1060 molecules. To bridge this vast gap, organic chemists are spearheading innovative methodologies that promise to broaden this limited chemical diversity. A beacon of this progressive wave is Asymmetric Carbene Transfer (ACT), a burgeoning strategy that significantly boosts molecular diversity with efficient bond-formation and precise chiral control. This review focuses on the capabilities of ACT in creating pharmaceutically significant molecules, encompassing an array of natural products and bioactive compounds. Through the lens of ACT, we discern its substantial influence on drug discovery, paving the way for novel therapeutic avenues by expanding the boundaries of molecular diversity. This review will shed light on prospective methodological developments of ACT and articulate their conceivable contributions to the medicinal chemistry arena.

Reinvestigation of clopidogrel bioactivation unveils new cytochrome P450-catalyzed thioester cleavage mechanism

The serendipitous prodrug clopidogrel (CPG, M0) is the mainstay antiplatelet drug in clinical use. The thiophene moiety of CPG undergoes ring opening to form the active metabolite (M13) through two steps of cytochrome P450 (CYP)-catalyzed oxidation. The stable intermediate resulting from the first oxidation, 2-oxo-CPG (M2), is proposed to be oxidized to form an S-oxide intermediate (M11), which proceeds with a hydrolytic pathway to yield a sulfenic acid (M12) and subsequently the bioreduced active metabolite (M13). To test the long-standing pathway of M2 to M13 via M11, we have chemically synthesized M11 but found it does not undergo the proposed hydrolytic activation in various conditions including in liver microsomal incubations. To seek an alternative mechanism, ¹⁸O tracing studies were performed with both H₂¹⁸O and ¹⁸O₂, and LC-MS studies show that the carboxylate product moiety acquires its O-atom from oxygen instead of water, which rules out M11 as the bioactivation intermediate. To explain the ¹⁸O tracing results, a one-step Baeyer-Villiger-like mechanism is proposed for the CYP-dependent thioester cleavage, which features the incorporation of the two O-atoms of O₂ into the two product moieties of carboxylate and sulfenic acid. The research presented herein provides a biochemical basis for delineating the clinical pharmacology of a mainstay treatment and expands our understanding of CYP catalysis.

Recent advances in the synthesis of organic chloramines and their insights into health care

Organic nitrogen–chlorine compounds and their derivatives are important heterocyclic motifs, exhibiting applications such as N-chlorinating agents, analytical reagents, disinfectants, antipathogens, and as synthetic intermediates for drugs, polymers, and natural products.

Enantioselective Synthesis of a Tricyclic, sp3 -Rich Diazatetradecanedione: an Amino Acid-Based Natural Product-Like Scaffold

6-, 7-, and 8-membered rings are assembled from a linear precursor by successive cyclisation reactions to construct a tricyclic diazatricyclo[6.5.1.04, 9 ]-tetradecanedione scaffold. Advanced building blocks based on d-aspartic acid and l-pyroglutamic acid were combined by a sp3 -sp2 Negishi coupling. A carbamate-guided syn-diastereoselective epoxidation followed by an intramolecular epoxide opening allowed the construction of the piperidine ring. An efficient one-pot hydroxyl-group protection twofold deprotection reaction prepared the ground for the cyclisation to the bicycle. A final deprotection of the orthogonal protecting groups and lactamisation led to the novel, sp3 -rich tricycle. The final compound is a substrate mimic of peptidyl-prolyl cis-trans isomerases featuring a locked trans-amide bond. Cheminformatic analysis of 179 virtual derivatives indicates favourable physicochemical properties and drug-like characteristics. As proof of concept we, show a low micromolar activity in a fluorescence polarisation assay towards the FK506-binding protein 12.

Simulation and experimental study on the mechanism of the chlorination of azithromycin

Azithromycin (AZI) has been listed as an emerging contaminant by the US EPA since 2009 because it is frequently detected in wastewater, surface water, and drinking water. In this paper, the chlorination of AZI in drinking water was simulated and studied. The results indicated that new compounds were generated in the chlorination of AZI. The byproducts were identified by liquid chromatography-quadrupole-time-of-flight mass spectrometry (LC-Q-TOF), and four of the byproducts were detected in real water samples. The kinetic studies demonstrated that the reaction rates of AZI chlorination were dependent on the initial concentration of free chlorine and the pH value. The potential toxicities of the byproducts were assessed by quantitative structure-activity relationship software and investigated by the viability of Chinese hamster lung (CHL), Jurkat T and Hep G2 cells.

Design, Synthesis, and Some Aspects of the Biological Activity of Mitochondria-Targeted Antioxidants

This review summarizes for the first time data on the design and synthesis of biologically active compounds of a new generation - mitochondria-targeted antioxidants, which are natural (or synthetic) p-benzoquinones conjugated via a lipophilic linker with (triphenyl)phosphonium or ammonium cations with delocalized charge. It also describes the synthesis of mitochondria-targeted antioxidants - uncouplers of oxidative phosphorylation - based on fluorescent dyes.

On the scope of oxidation of tertiary amines: Meisenheimer rearrangements versus Cope elimination in 2-(cyanoethyl)-2-azanorbornanes

When oxidized, exo-2-(cyanoethyl)-2-azanorbornene is prone to [1,2]-Meisenheimer rearrangement, its endo isomer undergoes [2,3]-Meisenheimer and exo/endo-2-(cyanoethyl)-2-azanorbornanes afford N-hydroxylamines through Cope elimination.

Hydrogen bond directed epoxidation: diastereoselective olefinic oxidation of allylic alcohols and amines

This article compares the diastereoselective epoxidation of acyclic and cyclic allylic alcohols, with the chemo- and diastereoselective olefinic oxidation of a range of acyclic and cyclic allylic amines. The diastereoselectivity in these systems is compared and a discussion about the origin of this high diastereocontrol is also presented. The ammonium directed epoxidation methodology has been extended to more complex substrates and representative applications of this protocol in natural product synthesis are also summarised.