Spectroscopic and Kinetic Evidence for the Crucial Role of Compound 0 in the P450cam‐Catalyzed Hydroxylation of Camphor by Hydrogen Peroxide

The hydroperoxo iron(III) intermediate P450_camFe^III–OOH, being the true Compound 0 (Cpd 0) involved in the natural catalytic cycle of P450_cam, could be transiently observed in the peroxo‐shunt oxidation of the substrate‐free enzyme by hydrogen peroxide under mild basic conditions and low temperature. The prolonged lifetime of Cpd 0 enabled us to kinetically examine the formation and reactivity of P450_camFe^III–OOH species as a function of varying reaction conditions, such as pH, and concentration of H₂O₂, camphor, and potassium ions. The mechanism of hydrogen peroxide binding to the substrate‐free form of P450_cam differs completely from that observed for other heme proteins possessing the distal histidine as a general acid–base catalyst and is mainly governed by the ability of H₂O₂ to undergo deprotonation at the hydroxo ligand coordinated to the iron(III) center under conditions of pH≥p${K{{{\rm P450}\hfill \atop {\rm a}\hfill}}}$ . Notably, no spectroscopic evidence for the formation of either Cpd I or Cpd II as products of heterolytic or homolytic O?O bond cleavage, respectively, in Cpd 0 could be observed under the selected reaction conditions. The kinetic data obtained from the reactivity studies involving (1R)‐camphor, provide, for the first time, experimental evidence for the catalytic activity of the P450Fe^III–OOH intermediate in the oxidation of the natural substrate of P450_cam.     

Metal–Organic Frameworks Based Electrocatalysts for the Oxygen Reduction Reaction

In view of the clean and sustainable energy, metal–organic frameworks (MOFs) based materials, including pristine MOFs, MOF composites, and their derivatives are emerging as unique electrocatalysts for oxygen reduction reaction (ORR). Thanks to their tunable compositions and diverse structures, efficient MOF‐based materials provide new opportunities to accelerate the sluggish ORR at the cathode in fuel cells and metal–air batteries. This Minireview first provides some introduction of ORR and MOFs, followed by the classification of MOF‐based electrocatalysts towards ORR. Recent breakthroughs in engineering MOF‐based ORR electrocatalysts are highlighted with an emphasis on synthesis strategy, component, morphology, structure, electrocatalytic performance, and reaction mechanism. Finally, some current challenges and future perspectives for MOF‐based ORR electrocatalysts are also discussed.     

Palladium/Norbornene‐Catalyzed Indenone Synthesis from Simple Aryl Iodides: Concise Syntheses of Pauciflorol F and Acredinone A

To show the synthetic utility of palladium/norbornene (Pd/NBE) cooperative catalysis, here we report concise syntheses of indenone‐based natural products, pauciflorol F and acredinone A, which are enabled by direct annulation between aryl iodides and unsaturated carboxylic acid anhydrides. Compared to the previous indenone‐preparation approaches, this method allows simple aryl iodides to be used as substrates with complete control of the regioselectivity. The total synthesis of acredinone A features two different Pd/NBE‐catalyzed ortho acylation reactions for constructing penta‐substituted arene cores, including the development of a new ortho acylation/ipso borylation.     

The Role of Organic Synthesis in the Emergence and Development of Antibody–Drug Conjugates as Targeted Cancer Therapies

With a number of antibody–drug conjugates (ADCs) approved for clinical use as targeted cancer therapies and numerous candidates in clinical trials, the field of ADCs is emerging as one of the frontiers in biomedical research, particularly in the area of cancer treatment. Chemists, biologists and clinicians, among other scientists, are partnering their expertise to improve their design, synthesis, efficacy and precision as they strive to advance this paradigm of personalized and targeted medicine to treat cancer patients more effectively and to expand its scope to other indications. Just as Alexander Fleming's penicillin, and the myriad other bioactive natural products that followed its discovery and success in the clinic, ignited a revolution in medicine after the Second World War, so did calicheamicin γ₁^I, and other highly potent naturally occurring antitumor agents, play a pivotal role in enabling the advent of this new paradigm of “biological‐small molecule hybrid” medical intervention. Today there are four clinically approved drugs from the ADC paradigm, Mylotarg, Adcetris, Kadcyla and Besponsa, in order of approval, the first and the last of which carry the same calicheamicin γ₁^I‐derived payload. Covering oncological applications, and after a brief history of the emergence of the field of antibody–drug conjugates triggered more than a century ago by Paul Ehrlich's “magic bullet” concept, this Review is primarily focusing on the chemical synthesis aspects of the ADCs multidisciplinary research enterprise.