The Diels-Alder (DA) reaction is a cornerstone of synthesis, yet Nature does not use catalysts for intermolecular [4+2] cycloadditions. Attempts to create artificial "Diels-Alderases" have also met with limited success, plagued by product inhibition. Using a simple PdL capsule we now show DA catalysis that combines efficient turnover alongside enzyme-like hallmarks. This includes excellent activity (k/k > 10), selective transition-state stabilization comparable to the most proficient DA catalytic antibodies, and control over regio- and chemoselectivity that would otherwise be difficult to achieve using small-molecule catalysts. Unlike other catalytic approaches that use synthetic capsules, this method is not defined by entropic effects; instead multiple H-bonding interactions modulate reactivity, reminiscent of enzymatic action.
The release of cytochrome c from mitochondria is a crucial step in apoptosis, resulting in the activation of the caspase proteases. A further consequence of cytochrome c release is the enhanced mitochondrial production of superoxide radicals (O 2 . ), which are converted to hydrogen peroxide by manganese-superoxide dismutase. Recently, we showed that cytochrome c is a potent catalyst of 2,7-dichlorofluorescin oxidation to the fluorescent 2,7-dichlorofluorescein by these species, leading to the conclusion that 2,7-dichlorofluorescein fluorescence is a reflection of cytosolic cytochrome c concentration rather than "reactive oxygen species" levels (Burkitt, M. J., and Wardman, P.
The biosynthesis of the meroterpenoid guajadial was previously hypothesized to occur via a hetero-Diels-Alder reaction between caryophyllene and an o-quinone methide. This hypothesis has been verified via the biomimetic synthesis of guajadial and psidial A in an aqueous three-component coupling reaction, between caryophyllene, benzaldehyde, and diformylphloroglucinol.
A synthesis fit for a king: The total synthesis of (±)‐kingianins A, D, and F has been achieved in ten steps. Key features include the gram‐scale synthesis and partial reduction of a conjugated tetrayne to a (Z,Z,Z,Z)‐tetraene, the domino 8π–6π electrocyclic ring closure of a (Z,Z,Z,Z)‐tetraene, and the radical‐cation‐catalyzed formal Diels–Alder dimerization of functionalized bicyclo[4.2.0]octadiene precursors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.