Bioinspired Asymmetric Synthesis of (−)-Gymnothelignan V

Total Synthesis of Gymnothelignan K via a One-Pot Homologative γ-Butyrolactonization

The first total synthesis of tetrahydrofuran dilignan gymnothelignan K is disclosed. The approach is based on implementing an early stage one-carbon homologative lactonization, which we recently disclosed, for constructing the γ-butyrolactone scaffold with the requisite β,γ-trans-vicinal stereocenters. Other salient features of the synthesis include the acid-promoted dimerization and the Suzuki-Miyaura cross-coupling reaction to install the challenging diaryl skeleton that permits the effective assembly of the optically active gymnothelignan K in 8 steps from commercially available materials.

Total Asymmetric Synthesis and Stereochemical Confirmation of (+)- and (-)-Lyoniresinol and Its Deuterated Analogues

Lyoniresinol and its derivatives are lignans which have been isolated from a plethora of plant species. In addition to exhibiting a range of interesting biological activities including anticancer, anti-inflammatory, antimicrobial, and others, these compounds have also been discovered in wines and spirits and shown to have gustatory effects in these alcoholic matrices. (+)-Lyoniresinol 1 is reported to impart a strong bitter taste while its enantiomer (-)-lyoniresnol 2 is tasteless. The first total asymmetric synthesis of both natural enantiomers (+)-1 and (-)-2 and their deuterated analogues (D₄)-(+)-3 and (D₄)-(-)-4 has been achieved, confirming the structure and stereochemistry of the natural products. The synthesized compounds can be utilized as internal standards in stable isotope dilution analysis for improving and optimizing the existing lyoniresinol quantitation methods in the future.

Total Synthesis of Oxepin and Dihydrooxepin Containing Natural Products

The construction of oxepin and dihydrooxepin containing natural products represents a challenging task in total synthesis. In the last decades, a variety of synthetic methods have been reported for the installation of these structural motifs. Herein, we provide an overview of synthetic methods and strategies to construct these motifs in the context of natural product synthesis and highlight the key steps of each example.

Construction of polycyclic bridged indene derivatives by a tandem 1,3-rearrangement/intramolecular Friedel-Crafts cyclization of propargyl acetates

An unprecedented Lewis acid-catalyzed cascade 1,3-rearrangement/Friedel-Crafts cyclization of propargyl acetates is developed for the construction of polycyclic bridged indene derivatives in moderate to good yields. This practical procedure features mild conditions, broad substrate scope, and easy operation.

Two new lignans from Gymnotheca involucrata

A new dibenzocyclooctdiene (1), and a new eupodienone (2) type lignans were isolated along with five known analogues from the whole plant of Gymnotheca involucrata Pei. The structures of the new compounds were elucidated on the basis of detailed spectroscopic analysis. Bioassay results showed that compounds 1 and 2 exhibited no antimicrobial activity against four Gram-positive bacterial strains and four Gram-negative bacteria at the concentration of 1 mg/mL.

Advances in the Synthesis of Lignan Natural Products

Lignans comprise a family of secondary metabolites existing widely in plants and also in human food sources. As important components, these compounds play remarkable roles in plants' ecological functions as protection against herbivores and microorganisms. Meanwhile, foods rich in lignans have revealed potential to decrease of risk of cancers. To date, a number of promising bioactivities have been found for lignan natural products and their unnatural analogues, including antibacterial, antiviral, antitumor, antiplatelet, phosphodiesterase inhibition, 5-lipoxygenase inhibition, HIV reverse transcription inhibition, cytotoxic activities, antioxidant activities, immunosuppressive activities and antiasthmatic activities. Therefore, the synthesis of this family and also their analogues have attracted widespread interest from the synthetic organic chemistry community. Herein, we outline advances in the synthesis of lignan natural products in the last decade.