Synthesis of 4-Alkylated Isocoumarins via Pd-Catalyzed α-Arylation Reaction

Polyketide- and Terpenoid-Derived Metabolites Produced by a Marine-Derived Fungus, Peroneutypa sp

Bioassay-guided investigation of the EtOAc-soluble extract of a culture of the marine-derived fungus Peroneutypa sp. M16 led to the isolation of seven new polyketide- and terpenoid-derived metabolites (1, 2, 4-8), along with known polyketides (3, 9-13). Structures of compounds 1, 2, and 4-8 were established by analysis of spectroscopic data. Absolute configurations of compounds 1, 2, 4, 6, 7, and 8 were determined by the comparison of experimental ECD spectra with calculated CD data. Compound 5 exhibited moderate antiplasmodial activity against both chloroquine-sensitive and -resistant strains of Plasmodium falciparum.

Ketones as strategic building blocks for the synthesis of natural product-inspired compounds

Natural product-inspired compound collections serve as excellent sources for the identification of new bioactive compounds to treat disease. However, such compounds must necessarily be more structurally-enriched than traditional screening compounds, therefore inventive synthetic strategies and reliable methods are needed to prepare them. Amongst the various possible starting materials that could be considered for the synthesis of natural product-inspired compounds, ketones can be especially valuable due to the vast variety of complexity-building synthetic transformations that they can take part in, their high prevalence as commercial building blocks, and relative ease of synthesis. With a view towards developing a unified synthetic strategy for the preparation of next generation bioactive compound collections, this review considers whether ketones could serve as general precursors in this regard, and summarises the opulence of synthetic transformations available for the annulation of natural product ring-systems to ketone starting materials.

Modular synthesis of 3-substituted isocoumarins via silver-catalyzed aerobic oxidation/6-endo heterocyclization of ortho-alkynylbenzaldehydes

A method involving silver-catalyzed aerobic oxidation/6-endo heterocyclization of ortho-alkynylbenzaldehydes to yield 3-substituted isocoumarins is described. The developed protocol allows convenient access to a range of synthetically useful 3-substituted isocoumarins and related fused heterocyclolactones in good to high yields, using silver tetrafluoroborate as the catalyst, and atmospheric oxygen as the terminal oxidant and the source of endocyclic oxygen. Mechanistic studies suggest the involvement of a free-radical pathway.

N-Heterocyclic carbene complexes enabling the α-arylation of carbonyl compounds

The considerable importance of α-arylated carbonyl compounds, which are widely used as final products or as key intermediates in the pharmaceutical industry, has prompted numerous research groups to develop efficient synthetic strategies for their preparation in recent decades. In this context, the α-arylation of carbonyl compounds catalyzed by transition-metal complexes have been particularly helpful in constructing this motif. As illustrated in this contribution, tremendous advances have taken place using palladium- and nickel-NHC (NHC = N-heterocyclic carbene) complexes as pre-catalysts for the arylation of a wide range of ketones, aldehydes, esters and amides with electron-rich, electron-neutral, electron-poor, and sterically hindered aryl halides or pseudo-halides. Despite significant progress, especially in asymmetric α-arylations promoted by chiral NHC ligands, there are numerous challenges which have and continue to encourage further studies on this topic. Some of these are presented in this report.

Genome Mining Discovery of a C4-Alkylated Dihydroisocoumarin Pathway in Fungi

A fungal C₄-alkylated dihydroisocoumarin pathway was discovered and elucidated. This pathway includes the following (1) a nonreducing polyketide synthase and a P450 collaboratively synthesize hydroxylated C₃-methylated isocoumarin 3; (2) a methyltransferase methylates 3 to 8; and (3) importantly, an esterase specifically catalyzes a ring reconstruction process of 8 to C₄-alkylated dihydroisocoumarin 10. Our discovery fills the gap in the enzymatic transformation process of natural C₄-alkylated isocoumarin derivates.