Establishment of Benzodioxazine Core Structure for Sarcodonin Class of Natural Products by X-ray Analysis

Diastereoselective synthesis of glycopyrans 1,2-annulated with dioxazinanes from 1,2-anhydrosugars and N-substituted nitrones

1,2-Annulated pyranose sugars fused with six membered rings have emerged as an important class of carbohydrates with wide biological and synthetic utility. We now describe zinc chloride catalyzed one pot diastereoselective synthesis of sugar fused dioxazinanes from 1,2-anhydro sugars and N-substituted aromatic nitrones. Various aromatic nitrones with different substituents undergo the reaction smoothly. The developed strategy works well with both ester and ether protection on the sugar and proceeds under mild reaction conditions. The mechanism seems to involve activation of the anhydrosugar by ZnCl₂ for nucleophilic attack by the nitrone followed by cyclization.

Natural Products with Heteroatom-Rich Ring Systems

This review focuses on all known natural products that contain a "heteroatom-rich" ring system, specifically a five-, six- or seven-membered ring that contains three or more heteroatoms. The isolation and biological activity of these natural products is discussed, along with the biosynthetic processes that Nature employs to assemble these rare heterocyclic frameworks.

Domino ring-opening cyclization (DROC) of activated aziridines and epoxides with nitrones via dual-catalysis “on water”

A simple and green approach for the synthesis of non-racemic 1,2,4-oxadiazinanes and 1,4,2-dioxazinanes with excellent yields (up to 99%) and stereoselectivity (de/ee > 99%) in water has been described.

Selected terpenoids from medicinal plants modulate endoplasmic reticulum stress in metabolic disorders

Objectives

The majority of research performed on cellular stress and apoptosis focuses on mitochondrial dysfunction; however, the importance of the endoplasmic reticulum dysfunction and the link to metabolic diseases has gained a substantial interest. This review focuses on the potential of terpenoids to influence endoplasmic reticulum stress and the possible role terpenoids play as the treatment of metabolic diseases.

Key findings

Metabolic diseases develop as a result of a cascade of cellular pathways. In most cases, cells are able to compensate for the disruption of the cellular homeostasis although the initiation of response pathways; however, chronic stress initiates apoptotic pathways. This reviewed (1) showed the importance of phytoterpenoids to influence endoplasmic reticulum (ER) stress and homeostasis, (2) showed how regulating ER stress affect the cell survival and death, and (3) highlighted some examples of how the progression of metabolic diseases can be influenced by ER.

Summary

Due to the substantial number of terpenoids that have been identified in literature, this review gave examples of 21 terpenoids that have been documented to have an effect on the different proteins associated with ER stress, how these plant terpenoids influence ER dysfunction and metabolic diseases such as diabetes, cancer, liver, and neurological diseases and parasitic infections.

Two sarcoviolins with antioxidative and α-glucosidase inhibitory activity from the edible mushroom Sarcodon leucopus collected in Tibet

Edible mushrooms are known as an important source of natural antioxidants. The ethyl acetate extract of the edible mushroom Sarcodon leucopus (Zangzi mushroom) possesses strong antioxidative activity. Bioactivity-guided isolation afforded 10 compounds from its fruiting bodies, including two new sarcoviolins, sarcoviolin β (1) and episarcoviolin β (2), and one new p-terphenyl derivative (3) along with seven known compounds. The structures of the new compounds were elucidated by spectroscopic methods and comparison with the known compounds. Compounds 1-10 were found to have antioxidant effects in the DPPH scavenging assay, the total antioxidant capacity assay, the reducing power assay, and the lipid peroxidation assay. Further study indicated that they could protect DNA strands from free radical-induced cleavage at 200 μM. Compounds 1-10 also presented strong α-glucosidase inhibitory activity. Of all tested compounds, compound 1 exhibited the strongest inhibitory activity, with an IC50 value of 0.58 μM.

Convergent synthesis and structural confirmation of phellodonin and sarcodonin ε

The first synthesis of members of the sarcodonin family, phellodonin and sarcodonin ε, is reported herein. This verifies that the unprecedented and seemingly unstable N,N-dioxide-containing benzodioxazine framework can be constructed in the laboratory and lends further support to the proposed structures. The key step in the synthesis involves a biomimetic hetero-Diels-Alder reaction between a pyrazine N-oxide and an ortho-quinone.