Total Synthesis of Varitriol, Varioxirane, and Enantiomer of the Proposed Biosynthetic Precursor

Benzyl Alcohol/Salicylaldehyde-Type Polyketide Metabolites of Fungi: Sources, Biosynthesis, Biological Activities, and Synthesis

Marine microorganisms are an important source of natural polyketides, which have become a significant reservoir of lead structures for drug design due to their diverse biological activities. In this review, we provide a summary of the resources, structures, biological activities, and proposed biosynthetic pathways of the benzyl alcohol/salicylaldehyde-type polyketides. In addition, the total syntheses of these secondary metabolites from their discoveries to the present day are presented. This review could be helpful for researchers in the total synthesis of complex natural products and the use of polyketide bioactive molecules for pharmacological purposes and applications in medicinal chemistry.

Visible-Light-Induced Pd-Catalyzed Radical Strategy for Constructing C-Vinyl Glycosides

A novel visible-light-induced palladium-catalyzed Heck reaction for bromine sugars and aryl olefins with high regio- and stereochemistry selectivity for the preparation of C-glycosyl styrene is described. This reaction takes place in one step at room temperature by using a simple and readily available starting material. This protocol can be scaled up to a wide range of glycosyl bromide donors and aryl olefin substrates. Mechanistic studies indicate that a radical addition pathway is involved.

A dual role for acetohydrazide in Pd-catalyzed controlled C(sp3)–H acetoxylation of aldehydes

The palladium catalyzed aldehyde directed acetoxylation of C(sp³)–H bonds was realized by a transient directing group approach for the first time.

Stereoselective Access to the Core Structure of Macroline-Type Indole Alkaloids: Total Synthesis of Macroline and Alstomicine

Rapid synthesis of the pentacyclic core structure of macroline-type indole alkaloids, and its application in the total synthesis of macroline and alstomicine is described. The core structure was accomplished in a highly stereocontrolled manner via two key steps, Ireland-Claisen rearrangement and Pictet-Spengler cyclization, commencing from a readily available starting material l-tryptophan, which obviated the need of a particular chiral source as an external catalyst, reagent, or internal auxiliary.

ZnBr2-catalyzed directC-glycosylation of glycosyl acetates with terminal alkynes

C-Alkynyl glycosides were synthesizedviaZnBr₂-catalyzed cross-coupling of glycosyl acetates with terminal alkynes.

Polyketide derivatives from a marine-sponge-associated fungus Pestalotiopsis heterocornis

Twelve previously undescribed polyketide derivatives, heterocornols A-L, and seven known analogues were isolated from a culture of the fungus Pestalotiopsis heterocornis associated with sponge. Their structures were elucidated by a comprehensive spectroscopic data analysis and CD Cotton effects. These compounds were evaluated for cytotoxic and antibacterial activities in vitro. Among them, heterocornols A-C, F-H, methyl-(2-formyl-3-hydroxyphenyl)propanoate, agropyrenol, and vaccinol G exhibited cytotoxicities against four human cancer cell lines with IC₅₀ values 15-100 μM, and they also showed antibacterial activities against Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis with MIC values ranging from 25 to 100 μg/mL. Moreover, compounds heterocornol C, heterocornol G, agropyrenol, and vaccinol G showed weak antifungal activities against Candida parapsilosis and Cryptococcus neoformans with MIC values 100 μg/mL.

Varioxiranols A-G and 19-O-Methyl-22-methoxypre-shamixanthone, PKS and Hybrid PKS-Derived Metabolites from a Sponge-Associated Emericella variecolor Fungus

Chemical examination of a sponge (Cinachyrella sp.)-associated Emericella variecolor fungus resulted in the isolation of seven new polyketide derivatives, namely, varioxiranols A-G (1-7), and a new hybrid PKS-isoprenoid metabolite, 19-O-methyl-22-methoxypre-shamixanthone (8), together with nine known analogues. Their structures were elucidated on the basis of extensive spectroscopic analyses, including ECD effects, Mosher's method, X-ray diffraction, and chemical conversion for the determination of absolute configurations. Varioxiranols F and G were found for the first time to link a xanthone moiety with a benzyl alcohol via an ether bond, while the dioxolanone group of 5 is unusual in nature. A cell-based lipid-lowering assay revealed that pre-shamixanthone (12) exerted significant inhibition against lipid accumulation in HepG2 cells without cytotoxic effects, accompanying the potent reduction of total cholesterol and triglycerides. Real-time quantitative PCR indicated that pre-shamixanthone (12) mediated the reduction of lipid accumulation related to the down-regulation of the expression of the key lipogenic transcriptional factor SREBP-1c and its downstream genes encoding FAS and ACC.