Hydroxylated Daphniphyllum Alkaloids from Daphniphyllum himalense

Total Synthesis of Four Classes of Daphniphyllum Alkaloids

The macrodaphniphyllamine-type, calyciphylline A-type, daphnilongeranin A-type, and daphnicyclidin D-type alkaloids are four structurally related classes of Daphniphyllum alkaloids. On the basis of a systematic analysis of the biogenetic network of these classes, we developed synthetic strategies centered on the C4-N and C1-C8 bonds of calyciphylline A, which took full advantage of the suitable substrates, reactions, and pathways that are altered from their counterparts in the postulated biogenetic network. Through this generalized biomimetic approach, we achieved the first synthesis of 14 Daphniphyllum alkaloids from the four subfamilies.

The chemistry of Daphniphyllum alkaloids

The triterpenoids Daphniphyllum alkaloids share the unique fused hexacyclic ring framework are isolated from the genus Daphniphyllum. These natural products possess comprehensive biological activities and exhibit excellent potential medicinal appliment. This review covers the reported isolation studies and biological activities of Daphniphyllum alkaloids spanning the period from 1966 to the beginning of 2020, In the meantime, the total synthesis of Daphniphyllum alkaloids will be emphatically summarized for supplement over this review series.

Daphnillonins A and B: Alkaloids Representing Two Unknown Carbon Skeletons from Daphniphyllum longeracemosum

Two highly rearranged daphniphyllum alkaloids, daphnillonins A (1) and B (2), were isolated from Daphniphyllum longeracemosum and structurally characterized by a combination of diverse methods, including the calculation of electronic circular dichroism. Compound 1 possesses an unprecedented carbon architecture with a very unique 8-methyl-6-azabicyclo[3.2.1]octane moiety, and compound 2 represents a new carbon skeleton with an uncommon 7/6/5/7/5/5-fused ring system. The biosynthetic pathways for the two alkaloids were proposed with the concurrent major alkaloids as the precursors.

Integrating yeast chemical genomics and mammalian cell pathway analysis

Chemical genomics has been applied extensively to evaluate small molecules that modulate biological processes in Saccharomyces cerevisiae. Here, we use yeast as a surrogate system for studying compounds that are active against metazoan targets. Large-scale chemical-genetic profiling of thousands of synthetic and natural compounds from the Chinese National Compound Library identified those with high-confidence bioprocess target predictions. To discover compounds that have the potential to function like therapeutic agents with known targets, we also analyzed a reference library of approved drugs. Previously uncharacterized compounds with chemical-genetic profiles resembling existing drugs that modulate autophagy and Wnt/β-catenin signal transduction were further examined in mammalian cells, and new modulators with specific modes of action were validated. This analysis exploits yeast as a general platform for predicting compound bioactivity in mammalian cells.

Highly Chemo-, Regio- and E/Z-Selective Intermolecular Heck-Type Dearomative [2 + 2 + 1] Spiroannulation of Alkyl Bromoarenes with Internal Alkynes

Described herein is a palladium-catalyzed dearomative annulation of alkyl bromoarenes with internal alkynes. Challenges in this spiroannulation include the chemoselectivity among [2 + 2 + 1], [2 + 2 + 2], and [3 + 2] annulations and the E/ Z-selectivity associated with the generated exocyclic double bond. In the presence of Pd(OAc)₂ and a phosphine ligand, a variety of highly functionalized spirocyclopentadienes with an exocyclic carbon-carbon double bond are provided in good to excellent yields with high chemo-, regio-, and E/ Z-selectivity via a Heck-type pathway.

Pd(ii)-Catalyzed [3 + 2] spiroannulation of α-aryl-β-naphthols with alkynes via a C–H activation/dearomatization approach

A Pd(ii)-catalyzed [3 + 2] spiroannulation of α-aryl-β-naphthols with internal alkynes has been developed by relying on a C–H activation/arene dearomatization approach.

Protein tyrosine phosphatase 1B inhibitors from natural sources

Since PTP1B enzyme was discovered in 1988, it has captured the research community's attention. This landmark discovery has stimulated numerous research studies on a variety of human diseases, including cancer, inflammation, and diabetes. Tremendous progress has been made in finding PTP1B inhibitors and exploring PTP1B regulatory mechanisms. This review investigates for the natural PTP1B inhibitors, and focuses on the common characteristics of the discovered structures and structure-activity relationships. To facilitate understanding, all the natural compounds are here divided into five different classes (fatty acids, phenolics, terpenoids, steroids, and alkaloids), according to their skeletons. These PTP1B inhibitors of scaffold structures could serve as a theoretical basis for new concept drug discovery and design.

Construction of the [6,5,7,5] Tetracyclic Core of Calyciphylline A Type Alkaloids via a Tandem Semipinacol Rearrangement/Nicholas Reaction

A novel and efficient approach toward the assembly of the synthetically challenging tetracyclic [6,5,7,5] core structure of calyciphylline A-type alkaloids is developed. The synthetic route features a tandem semipinacol rearrangement/Nicholas reaction that has been devised strategically to construct the spirocyclic A/B ring and the sterically congested vicinal all-carbon quaternary carbon centers in high diastereoselectivity. Late-stage installation of the hydropyrrole ring and the strained 7-membered ring via a double-reductive amination and ring-closing metathesis, respectively, has also been realized.

Palladium(0)-catalyzed [2 + 2 + 1] cyclization of 1,6-enynes with vinyl bromides: a highly diastereoselective synthesis of tetrahydro-1H-cyclopenta[c]furans bearing two quaternary carbon centers

A new cascade process has been accomplished for the synthesis of tetrahydro-1H-cyclopenta[c]furans through palladium-catalyzed [2 + 2 + 1] cyclization of 1,6-enynes with vinyl bromides. Notably, the key feature of this transformation is the use of vinyl bromides as the C1 building block. Various functionalized tetrahydro-1H-cyclopenta[c]furans bearing two quaternary carbon centers could be obtained in good yields with excellent diastereoselectivities.

Recent Progress in the Chemistry of Daphniphyllum Alkaloids †

Daphniphyllum is an evergreen species known since 1826. After initial systematic investigations, more than 320 members of this family have been isolated, which comprise complex and fascinating structures. Unique azapolycyclic architectures containing one or more quaternary stereocenters render these alkaloids synthetically challenging. This review covers efforts toward the synthesis of Daphniphyllum alkaloids spanning the period from 2005 to the beginning of 2016, including reported biological activities as well as the isolation of new members of this genus.

Eucarobustols A-I, Conjugates of Sesquiterpenoids and Acylphloroglucinols from Eucalyptus robusta

Nine new conjugates of sesquiterpenoids and acylphloroglucinols, named eucarobustols A-I (1-9), as well as 11 known analogues were isolated from the leaves of Eucalyptus robusta. The sesquiterpenoid motifs furnishing the new conjugates included four structural types of aristolane (1 and 2), guaiane (3), eudesmane (4), and aromadendrane (5-9) moieties. Compounds 1 and 2 were found to represent the first examples of conjugates of aristolane and acylphloroglucinol units. In turn, compound 3 features a new coupling model of guaiane and acylphloroglucinol via the C-4-C-7' bond. Compounds 1, 7, and 9 showed inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) with IC50 values of 1.3, 1.8, and 1.6 μM, respectively.

Palladium(0)-Catalyzed Intermolecular Carbocyclization of (1,n)-Diynes and Bromophenols: An Efficient Route to Tricyclic Scaffolds

A novel palladium(0)-catalyzed dearomative cyclization reaction of bromophenols with (1,n)-diynes has been developed for building two new types of tricyclic architectures containing a quaternary carbon center. This method employs inexpensive bromophenols, and easily accessible tethered diynes. It exhibits a broad substrate scope and tolerates various functional groups. Preliminary results with commercially available chiral ligands indicate that enantioselective variants are feasible for both cyclization processes.

Himalensines A and B, Alkaloids from Daphniphyllum himalense

Chemical investigation into the alkaloidal constituents of the Nepalese Daphniphyllum himalense has returned two new compounds, himalensines A (1) and B (2), with unprecedented carbon skeletons. Structures of the two alkaloids have been characterized on the basis of spectroscopic methods, especially via 2D NMR data analysis. Himalensine B (2) showed marginal inhibitory activities against two kinases, PTP1B and IKK-β.

New alkaloids from Daphniphyllum himalense

A series ofDaphniphyllumalkaloids with selective kinase inhibitory activity were isolated and structurally characterized fromDaphniphyllum himalense.