Facile Production Scale Synthesis of (S)-Taniguchi Lactone: A Precious Building-Block

Collective Total Synthesis of Ecklonialactones, Eiseniachlorides and Analogs

Ecklonialactones, Eiseniachlorides, and Egregiachlorides are synthesized in living organisms via the lipoxygenase-mediated oxidation of polyunsaturated fatty acids. Originally isolated and identified from brown seaweed (Ecklonia stolonifera, Eisenia bicyclis, and Egregia menziesii), and later replicated on milligram scale through chemical synthesis, the full biological activities of these compounds remain to be elucidated. To bridge this gap in knowledge, we propose a unified methodology to synthesize the 14-membered macrocyclic structures of Ecklonialactones, Eiseniachlorides and analogs using a versatile and convergent approach. This study delineates the synthesis of Ecklonialactone A, B, C, D, and Eiseniachlorides A and B, as well as ent-Ecklonialactone B, 16-epi-Ecklonialactone B and 12,13-diepi-Ecklonialactone B.

Furofuran Lignans for Plant Protection: Discovery of Sesamolin and Its Derivatives as Novel Anti-Tobacco Mosaic Virus and Antibacterial Agents

Natural products have been a valuable source of efficient and low-risk pesticides. In this work, a series of novel sesamolin derivatives A0-A31 and B0-B4 were designed and synthesized via structural simplification of furofuran lignan phrymarolin II, and their antiviral and antibacterial activities were systematically evaluated. The bioassay results showed that compound A24 displayed remarkable inactivation activity against tobacco mosaic virus (TMV) with an EC₅₀ value of 130.4 μg/mL, which was superior to that of commercial ningnanmycin (EC₅₀ = 202.0 μg/mL). The antiviral mode of action assays suggested that compound A24 may obstruct self-assembly by binding to TMV coat protein (CP), thus resisting the TMV infection. In addition, compound A25 possessed prominent antibacterial activities, especially against Ralstonia solanacearum with an EC₅₀ value of 43.8 μg/mL, which is better than those of commercial bismerthiazol and thiodiazole copper. This research lays a solid foundation for the utilization of furofuran lignans in crop protection.

Iridium-Catalyzed Asymmetric Cascade Allylation/Retro-Claisen Reaction

An enantiomerically enriched 3-hydroxymethyl pentenal unit is one of the key structural cores in plenty of natural products and drug candidates with significant biological activities. However, very few synthetic methodologies for the facile construction of the related skeletons have been reported to date. Herein, an elegant iridium-catalyzed asymmetric cascade allylation/retro-Claisen reaction of readily available β-diketones with VEC was successfully developed, and a wide range of functionalized chiral 3-hydroxymethyl pentenal derivatives could be prepared in good yields with excellent enantioselectivities. Various 1,3-diketones and functionalized ketones containing different electron-withdrawing groups on the β-position were well tolerated as outstanding partners with high reactivity and excellent regio-/chemo-/enantioselectivity. The synthetic utility of product chiral 3-hydroxymethyl pentenal derivatives was well shown through gram-scale transformation, hydrogenation, cyclopropanation, hydroboration, and olefin metathesis. Moreover, this elegant protocol demonstrated synthetic applications in the concise synthesis of synthetically useful chiral building block (S)-Taniguchi lactone and the formal synthesis of natural product cytisine. A rational reaction pathway was proposed based on the experimental results and control experiments.

Recent strategies and tactics for the enantioselective total syntheses of cyclolignan natural products

Covering: 2000 to 2021Lignan natural products are found in many different plant species and possess numerous useful biological properties, such as anti-inflammatory, antiviral, antioxidant, antibacterial, and antitumor activities. Their utility in both traditional and conventional medicine, coupled with their structural diversity has made them popular synthetic targets over many decades. This review specifically addresses the cyclolignan subclass of the family, which possess both a C8-C8' and a C2-C7' linkage between two different phenylpropene units. We present a comprehensive overview of the diverse strategies employed by chemists to achieve enantioselective total syntheses of cyclolignans covering: 2000 to 2021.

Scalable Total Synthesis of (-)-Triptonide: Serendipitous Discovery of a Visible-Light-Promoted Olefin Coupling Initiated by Metal-Catalyzed Hydrogen Atom Transfer (MHAT)

An efficient and scalable total synthesis of (-)-triptonide is accomplished based on a metal-catalyzed hydrogen atom transfer (MHAT)-initiated radical cyclization. During the optimization of the key step, we discovered that blue LEDs significantly promoted the efficiency of reaction initiated by Co(TPP)-catalyzed MHAT. Further exploration and optimization of this catalytic system led to development of a dehydrogenative MHAT-initiated Giese reaction.

Topical 'dual-soft' glucocorticoid receptor agonist for dermatology

Steroidal glucocorticoids (GR agonists) have been widely used for the topical treatment of skin disorders, including atopic dermatitis. They are a very effective therapy, but they are associated with both unwanted local effects in the skin (skin thinning/atrophy) and systemic side effects. These effects can limit the long-term utility of potent steroids. Here we report on a topically delivered non-steroidal GR agonist, that has the potential to deliver high efficacy in the skin, but due to rapid metabolism in the blood & liver ("dual-soft") it should have greater systemic safety than existing treatments. In addition, compared to less selective steroidal GR agonists, the new non-steroidal Selective Glucocorticoid Agonists (SEGRAs) have the potential to avoid the skin atrophy observed with existing topical steroids. Due to its potential for reduced skin atrophy and low systemic exposure, LEO 134310 (17) may be suitable for long term topical treatment of skin diseases such as atopic dermatitis and psoriasis.

Asymmetric total synthesis of (+)-ovafolinins A and B

(+)-Ovafolinins A and B are two homologous lignans containing unique polycyclic skeletons. Benefiting from a highly diastereoselective alkylation of (S)-Taniguchi lactone, a double Friedel-Crafts reaction, a global debenzylation and a Cu(OAc)₂-enabled benzylic oxidative cyclization, we present herein an efficient synthetic approach to (+)-ovafolinins A and B.

First chemo-enzymatic synthesis of the (R)-Taniguchi lactone and substrate profiles of CAMO and OTEMO, two new Baeyer-Villiger monooxygenases

ABSTRACT

This study investigates the substrate profile of cycloalkanone monooxygenase and 2-oxo-Δ³-4,5,5-trimethylcyclopentenylacetyl-coenzyme A monooxygenase, two recently discovered enzymes of the Baeyer-Villiger monooxygenase family, used as whole-cell biocatalysts. Biooxidations of a diverse set of ketones were performed on analytical scale: desymmetrization of substituted prochiral cyclobutanones and cyclohexanones, regiodivergent oxidation of terpenones and bicyclic ketones, as well as kinetic resolution of racemic cycloketones. We demonstrated the applicability of the title enzymes in the enantioselective synthesis of (R)-(-)-Taniguchi lactone, a building block for the preparation of various natural product analogs such as ent-quinine.

GRAPHICAL ABSTRACT