Vitrimers synthesized from epoxy-carboxylic acid-alkylamine (Cn) formulations exhibit tunable mechanical properties and stress relaxation without using external catalysts.

No abstract

New 1,8-dioxooctahydroxanthenes with substituents in the 2-, 3-, and 9-positions were obtained by cyclization with iodine from tandem Michael/Michael adducts. The X-ray molecular structure of the methyl 2- (1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)acetate (3a) was solved and shows

Two synthetic approaches towards the synthesis of the tetracyclic lactone 4, containing the caged bis(acetalic) backbone of Saudin, were explored. Both sequences included the utilization of the known epoxy-acetal 3, prepared stereoselectively by means of an intramolecular radical cyclization, as the common key intermediate, allowing total control over the

The phagodepression activity of five coumarins (= 2H-1-benzopyran-2-ones), 6-hydroxy-7-isoprenyloxycoumarin (1), 6-methoxy-7-isoprenyloxycoumarin (2), 6,7-methylenedioxycoumarin (3), 5-methoxy-6,7-methylenedioxycoumarin (4), and 6-methoxy-7-(2-hydroxyethoxy)coumarin (5), from the Argentine native herb Pterocaulon polystachyum, was tested against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae. Two analogs, scopoletin (6) and 2-methoxy-2-methyl-3,4,5,6,7,8-hexahydro-3H-chromen-5-one (7), synthesized in our laboratory, were also evaluated for comparison. The compounds were added to an artificial diet at doses ranging from 50 to 200 microg per g of diet. Natural coumarins induced 100% of phagodepression when 200 microg were added per g of diet. Binary equimolar mixtures of the natural coumarins were phagodepressors against S. frugiperda surpassing the expected additive responses, indicating that these compounds can act synergistically against S. frugiperda larvae. Compounds 1 and 3 (non-methoxylated coumarins), and the equimolar mixture of both, displayed the strongest phagodepression. Additionally, 50 microg/g of 1 and 3 incorporated to the larval diet caused 80 and 50% of pupal mortality, respectively, while a 100 microg/g dose of compounds 2, 4, 6, and 7 produced 60, 50, 10, and 80% pupal mortality, respectively. Larval growing rate during the early larval instars was significantly reduced by treatments with the methylenedioxycoumarins 3 and 4. Coincidentally, the larval period duration was significantly increased by the latter compounds.

The partial structure 2 of the bisketal-type, tetracyclic saudin (1), an important natural product, was de novo synthesized. A key step was the Jones oxidation of the epoxide 3, which gave rise to epoxide-ring opening, followed by acetal hydrolysis, alcohol oxidation, and, finally, intramolecular acetal formation. The resulting key intermediate was finally oxidized to the target lactone 2.

Intermolecular tandem-Michael/Michael addition reactions of alkyne acceptors and CH-acidic compounds such as 1,3-cyclohexanedione (2a) and dimedone (2b) under L-proline catalysis furnished four new products 1a-d with C 2 axial chirality.

We report the first solid-phase synthesis of (1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)acetic acids via a tandem Michael-Michael cyclization with resin-bound propiolic acid as Michael acceptor and cyclohexanediones.