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We have accomplished the total synthesis of sculponin U, a polycyclic C‐20‐oxygenated kaurane diterpenoid featuring a 7,20‐lactone‐hemiketal bridge, through a radical cascade cyclization triggered by photoinduced electron transfer (PET) of a silyl enolate to form the cyclohexanone‐fused bicyclo[3.2.1]octane skeleton. Other key points in our synthetic strategy encompass a Diels–Alder reaction to construct the middle six‐membered ring of sculponin U, and an intramolecular radical cyclization induced by iron‐catalyzed hydrogen atom transfer to close the western cyclohexane ring. Successful preparation of the enantiopure silyl enolate as the PET precursor enables the asymmetric total synthesis of sculponin U, opening a new avenue for divergent syntheses of structurally related C‐20‐oxygenated kaurane congeners and pharmaceutical derivatives thereof. [ABSTRACT FROM AUTHOR]

We report the first total synthesis of the monoterpene indole alkaloids ophiorrhine A via a late stage bioinspired intramolecular Diels–Alder cycloaddition to form the intricate bridged and spirannic polycyclic system. Several strategies were investigated to construct the indolopyridone moiety of ophiorrhiside E, the postulated biosynthetic precursor of ophiorrhine A. Eventually, the Friedel–Crafts‐type coupling of N‐methyl indolyl‐acetamide with a secologanin‐derived acid chloride delivered ophiorrhine G. Cyclodehydration of a protected form of the latter was followed by the desired spontaneous intramolecular Diels–Alder cycloaddition of protected ophiorrhiside E leading to ophiorrhine A. [ABSTRACT FROM AUTHOR]

We report the first total synthesis of the monoterpene indole alkaloids ophiorrhine A via a late stage bioinspired intramolecular Diels–Alder cycloaddition to form the intricate bridged and spirannic polycyclic system. Several strategies were investigated to construct the indolopyridone moiety of ophiorrhiside E, the postulated biosynthetic precursor of ophiorrhine A. Eventually, the Friedel–Crafts‐type coupling of N‐methyl indolyl‐acetamide with a secologanin‐derived acid chloride delivered ophiorrhine G. Cyclodehydration of a protected form of the latter was followed by the desired spontaneous intramolecular Diels–Alder cycloaddition of protected ophiorrhiside E leading to ophiorrhine A. [ABSTRACT FROM AUTHOR]

Melanosomes in nature have diverse morphologies, including spheres, rods, and platelets. By contrast, shapes of synthetic melanins have been almost entirely limited to spherical nanoparticles with few exceptions produced by complex templated synthetic methods. Here, we report a non‐templated method to access synthetic melanins with a variety of architectures including spheres, sheets, and platelets. Three 1,8‐dihydroxynaphthalene dimers (4‐4′, 2‐4′ and 2‐2′) were used as self‐assembling synthons. These dimers pack to form well‐defined structures of varying morphologies depending on the isomer. Specifically, distinctive ellipsoidal platelets can be obtained using 4‐4′ dimers. Solid‐state polymerization of the preorganized dimers generates polymeric synthetic melanins while maintaining the initial particle morphologies. This work provides a new route to anisotropic synthetic melanins, where the building blocks are preorganized into specific shapes, followed by solid‐state polymerization. [ABSTRACT FROM AUTHOR]

Keywords: allomelanin; anisotropy; DHN melanin; melanin; solid-state polymerization EN allomelanin anisotropy DHN melanin melanin solid-state polymerization 17221 17221 1 07/28/21 20210802 NES 210802 B Anisotropic synthetic melanins b have been generated by solid-state polymerization, as reported by Nathan C. Gianneschi et al. in their Research Article on page 17464. Ellipsoidal platelets of melanin, found to date only in biology, were obtained through pre-organizing the 4-4' dihydroxynaphthalene dimer as the building block, followed by solid-state oxidative polymerization to give polymeric melanin materials without changing their overall morphology. Ellipsoidal platelets of melanin, found to date only in biology, were obtained through pre-organizing the 4-4' dihydroxynaphthalene dimer as the building block, followed by solid-state oxidative polymerization to give polymeric melanin materials without changing their overall morphology. [Extracted from the article]