Stereoselective Total Synthesis of (+)-Nephrosteranic Acid and (+)-Roccellaric Acid through Asymmetric Dihydroxylation and Johnson-Claisen Rearrangement

Stereodivergent Synthesis of 1,4-Dicarbonyl Compounds through Sulfonium Rearrangement: Mechanistic Investigation, Stereocontrolled Access to γ-Lactones and γ-Lactams, and Total Synthesis of Paraconic Acids

Although simple γ-lactones and γ-lactams have received considerable attention from the synthetic community, particularly due to their relevance in biological and medicinal contexts, stereoselective synthetic approaches to more densely substituted derivatives remain scarce. The in-depth study presented herein, showcasing a straightforward method for the stereocontrolled synthesis of γ-lactones and γ-lactams, builds on and considerably expands the stereodivergent synthesis of 1,4-dicarbonyl compounds by a ynamide/vinyl sulfoxide coupling. A full mechanistic and computational study of the rearrangement was conducted, uncovering the role of all of the reaction components and providing a rationale for stereoselection. The broad applicability of the developed tools to streamlining synthesis is demonstrated by concise enantioselective total syntheses of (+)-nephrosteranic acid, (+)-rocellaric acid, and (+)-nephromopsinic acid.

Concise Stereoselective Synthesis of β-Hydroxy-γ-lactones: (4R,5R)-4-Hydroxy-γ-decalactone from the Japanese Orange Fly and Enantiomers of Arachnid Harvestmen Isolates

The naturally occurring (4R,5R)-4-hydroxy-γ-decalactone from the Japanese orange fly and the antipode of (4S,5R)-4-hydroxy-γ-dodecalactone from the harvestmen arachnid and their stereoisomers are synthesized from the chiral pool material d-glucono-δ-lactone in a few steps. The one-pot conversion of the latter to γ-vinyl-β-hydroxy-γ-lactone, cross-metathesis with requisite olefin, and hydrogenation enabled the synthesis of syn-lactones in just a two-pot operation. An additional efficient Pd-catalyzed allylic isomerization of γ-vinyl-β-hydroxy-γ-lactone led to the anti-lactones in high yields.

Enantioselective Total Synthesis of Mollebenzylanol A

Mollebenzylanol A is a tyrosine phosphatase 1B inhibitor isolated from the leaves of Rhododendron molle in 2018 that has a highly functionalized structure. The first enantioselective total synthesis of mollebenzylanol A was achieved in 13 steps from a known chiral starting material. An efficient and practical synthetic scheme was disclosed in a stereocontrolled manner, including stereo/regioselective epoxidation, Eschenmoser-Claisen rearrangement, and stereocontrolled dihydroxylation.

New paraconic acids from the endophytic fungus Xylariaceae sp. J4

Three new paraconic acids, xylariacinics A-C (1-3), were isolated from the endophyte Xylariaceae sp. J4 harbored in the medicinal plant Blumea balsamifera. Their structures were elucidated on the basis of extensive spectroscopic data including HRMS, and NMR. The antibacterial efficacies of compounds 1-3 were evaluated against a panel of bacteria such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa. Their antifungal activities were also tested against Colletotrichum gloeosporioides. Unfortunately, all of them were inactive.

A protecting-group-free synthesis of (+)-nephrosteranic, (+)-protolichesterinic, (+)-nephrosterinic, (+)-phaseolinic, (+)-rocellaric acids and (+)-methylenolactocin

A collective synthesis of a γ-butyrolactone class of paraconic acids such as (+)-methylenolactocin, (+)-phaseolinic acid, (+)-nephrosteranic acid, (+)-nephrosterinic acid, (+)-rocellaric acid and (+)-protolichesterinic acid is described.

Synthesis of aminomethyl derivatives of 5-substituted-3-(prop-2-ynyl)dihydrofuran-2(3H)-ones

An easy approach for the synthesis of various 5-substituted-3-(prop-2-ynyl)dihydrofuran-2(3H)-ones is described. As a method of choice, Mannich aminomethylation of terminal alkynes is adopted. The reaction works well with acyclic and cyclic secondary amines and provides the desired products, with good to very good yields.

A stereoselective synthesis of the reported structure of polyporolide

A concise stereoselective synthesis of the reported structure of newly isolated acetogenin polyporolide is presented indicating a need for structure revision of the natural product.

A concise protecting-group-free synthesis of cephalosporolides E and F

A concise protecting-group-free synthesis of cephalosporolides E and F has been accomplished from l-mannonic-γ-lactone by one-pot conversion to γ-vinyl-β-hydroxy-γ-lactone, cross-metathesis and Wacker-type oxidative spiroketalization.

Anti-HIV-1 tigliane diterpenoids from Excoecaria acertiflia Didr

Three tigliane-type diterpenoids named excoecafolins A-C and two daphnane-type diterpenoids named excoecafolins D and E, together with 13 known compounds, were isolated from the EtOAc extract of Excoecaria acerifolia Didr. Their structures were elucidated through the analysis of the spectroscopic data. The anti-HIV-1 activity evaluation of five of these compounds showed that four possessed moderate anti-HIV-1 activities with EC50 0.258, 0.036, 0.046, and 0.978 μM, SI >1,836.9, 431.1, 298.7, and >503.7, respectively. Additionally, the chemotaxonomic issue of the affinity correlation between Thymelaeceae and Euphorbiaceae is discussed based on the isolates.