Advances in the anti-tumor potential of hederagenin and its analogs.

Hederagenin is a pentacyclic triterpenoid that is widely distributed as the main pharmaceutical ingredient in various medicinal plants. Similarly as other pentacyclic triterpenoids, hederagenin has various pharmacological effects such as anti-tumor, anti-inflammatory, anti-depressant, and anti-viral activities. In particular, the anti-tumor activity of hederagenin indicates its potential for development into highly effective chemotherapeutic agents. Studies revealed that hederagenin effectively suppresses the growth of various tumor cell lines in vitro and interacts with several molecular targets that play essential roles in various cellular signaling pathways. The compound suppresses transformation, inhibits proliferation, and induces apoptosis in tumor cells. In this review, we highlight research progress on the source, pharmacokinetics, pharmacological activity, and mechanism of action of hederagenin and the anti-tumor activity of its analogs by integrating and analyzing relevant domestic and international studies and providing a basis for their further development and application.

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.

Dealkenylative Ni-Catalyzed Cross-Coupling Enabled by Tetrazine and Photoexcitation.

A new and general method to functionalize the C(sp3)-C(sp2) bond of alkyl and alkene linkages has been developed, leading to the dealkenylative generation of carbon-centered radicals that can be intercepted to undergo Ni-catalyzed C(sp3)-C(sp2) cross-coupling. This one-pot protocol leverages the easily procured alkene feedstocks for organic synthesis with excellent functional group compatibility without the need for a photoredox catalyst.

Enantioselective Total Synthesis of Pseudopteroxazole and Ileabethoxazole.

Enantioselective total syntheses of pseudopteroxazole (1) and ileabethoxazole (2) are presented. The two original stereocenters were constructed in excellent enantioselectivity and good diastereoselectivity through Carreira's asymmetric dual catalytic allylation, which shows potential for accessing diastereoisomers at C2 and C3 of 1 and 2. Cationic cyclizations of 13 and 24 demonstrated an effective pathway for the construction of the opposite configurations at C1 in 1 and 2. Additionally, an approach for the introduction of methyl at C4 is a feasible solution for structural modifications at C4 in 1 and 2.

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.

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.