Phosphine-catalyzed Divergent Domino Processes between γ-Substituted Allenoates and Carbonyl-Activated Alkenes

Concise synthesis of chiral γ-butenolides via an allylation/lactonization cascade reaction

A highly enantioselective allylation/lactonization cascade was developed, which provides a concise and efficient route to chiral γ-butenolides under mild conditions. Most of the reaction examples can be completed in 10 minutes with high selectivity.

Diastereodivergent and Regioselective Synthesis of Tetrahydrofuro[2,3-b]furans with Four Consecutive Stereocenters

Base-catalyzed diastereodivergent and regioselective domino processes of triketone enones with arylacetaldehydes for the synthesis of tetrahydrofuro[2,3-b]furans with four consecutive stereocenters are reported. Good yields and diastereoselectivities are obtained when DBU is employed as a catalyst; in contrast, Et3N delivers a different diastereomer in excellent diastereoselectivity. This work offers many advantages, including switchable diastereoselectivity, cheap base catalysts, and a simple operation.

Design, Synthesis, and Anti-Hepatocellular Carcinoma Evaluation of Sesquiterpene Lactone Epimers Trilobolide-6-O-isobutyrate Analogs

Hepatocellular carcinoma (HCC), one of the most common malignant cancers with a low 5-year survival rate, is the third leading cause of cancer-related deaths worldwide. The finding of novel agents and strategies for the treatment of HCC is an urgent need. Sesquiterpene lactones (SLs) have attracted extensive attention because of their potent antitumor activity. In this study, a new series of SL derivatives (3-18) were synthesized using epimers 1 and 2 as parent molecules, isolated from Sphagneticola trilobata, and evaluated for their anti-HCC activity. Furthermore, the structures of 4, 6, and 14 were confirmed by X-ray single-crystal diffraction analyses. The cytotoxic activities of 3-18 on two HCC cell lines, including HepG2 and Huh7, were evaluated using the CCK-8 assay. Among them, compound 10 exhibited the best activity against the HepG2 and Huh7 cell lines. Further studies showed that 10 induced cell apoptosis, arrested the cell cycle at the S phase, and induced the inhibition of cell proliferation and migration in HepG2 and Huh7. In addition, absorption, distribution, metabolism, and excretion (ADME) properties prediction showed that 10 may possess the properties to be a drug candidate. Thus, 10 may be a promising lead compound for the treatment of HCC.

Switchable multipath cascade cyclization to synthesize bicyclic lactams and succinimides via chemodivergent reaction

Herein, a novel switchable multipath cascade cyclization via chemodivergent reaction between readily available ketoamides and deconjugated butenolides was developed to efficiently synthesize γ-lactone fused γ-lactams and succinimide fused hemiketals. The Aldol/aza-Michael reaction and Aldol/imidation/hemiketalization reaction were enabled by catalytic amounts of two bases, namely tetramethyl guanidine and NaOAc. A wide range of substrate scope with diverse functional group compatibility was demonstrated to deliver the corresponding products with good yield and excellent diastereoselectivity (>60 examples).

Phosphine-Catalyzed Atroposelective Formal [3 + 2] Cycloaddition Desymmetrization of N-Arylmaleimides

Herein, a new strategy for the enantioselective synthesis of axially chiral N-aryl succinimides was devised by [3 + 2] annulation of MBH carbonates and N-aryl maleimides under chiral phosphine. This desymmetrization process allows for quick construction of both two stereogenic carbon centers and a remote C_Ar-N atropisomeric chirality. A series of structurally diverse N-aryl succinimides were obtained with good to excellent yields, diastereoselectivities, and enantioselectivities. The process is mild, efficient, and scalable and features a broad substrate scope.

Synthetic and Computational Study of the Enantioselective [3+2]-Cycloaddition of Chromones with MBH Carbonates

Highly efficient and straightforward access to enantioenriched five-membered ring-fused chromanones is developed via [3+2]-cycloaddition of 3-cyanochromones with Morita-Baylis-Hillman carbonates. Densely functionalized chiral cyclopenta[b]chromanones with three continuous quaternary and tertiary stereogenic carbon centers were obtained in high yields with high ee and dr (≤97% yield, 97% ee, and >20:1 dr). Moreover, density functional theory calculations have been carried out to investigate the mechanism and regio- and diastereoselectivity of the reaction.

Asymmetric Brønsted base-catalyzed aza-Michael addition and [3 + 2] cycloaddition reactions of N-ester acylhydrazones and enones

We reported the first enantioselective Brønsted base-catalyzed aza-Michael addition and stepwise cascade [3+2] cycloaddition between acylhydrazones and unsaturated ketones. The enantio-enriched aza-Michael adducts can be transformed into 2-pyrazolines.

Asymmetric cross Rauhut–Currier reactions of vinyl ketones with carbonyl para-quinone methides via phosphine catalysis

Novel cross Rauhut–Currier reactions, involving chiral phosphine catalysis, between vinyl ketones and terminal-carbonyl-substituted para-quinone methides are presented.