Naphthopyranones--isolation, bioactivity, biosynthesis and synthesis.

The 1H-naphtho[2,3-c]pyran-1-one (naphthopyranone) moiety forms the structural framework of a group of secondary metabolites that have been isolated from a range of organisms including fungi, bacteria, lichen and plants. This review documents the known naturally occurring naphthopyranones - their isolation, biosynthesis and biological activity. A survey of methods reported for the synthesis of naphthopyranone natural products is presented.

Exploring O-stannyl ketyl and acyl radical cyclizations for the synthesis of γ-lactone-fused benzopyrans and benzofurans.

The synthesis of a series of γ-lactone-fused benzopyrans and benzofurans, analogues of the pyranonaphthoquinone antibiotics, is reported. Preparation of the heterocycles was achieved by either O-stannyl ketyl or acyl radical cyclization of benzaldehyde precursors followed by oxidation to give the pyrano- and furanobenzoquinone systems. The observed diastereoselectivity during O-stannyl ketyl radical cyclization is influenced by aromatic substitution ortho to the aldehyde, whilst acyl radical cyclization followed by stereoselective reduction of the resulting pyranones provides a complimentary approach to forming the required γ-lactone-fused benzopyran systems.

Approach to the functionalized cyclopentane core of marine prostanoids by applying a radical cyclization of β-disubstituted acrylates.

A synthetic approach to highly functionalized cyclopentanes that incorporate adjacent secondary and tertiary alcohols is described. These systems, prepared in one step by a ketyl radical cyclization of β-disubstituted acrylates, represent the core of the marine prostanoid family of natural products.

Ketyl radical cyclization of β-disubstituted acrylates: formal syntheses of (+)-secosyrin 1 and longianone and the total synthesis of (+)-4-epi-secosyrin 1.

A novel approach to the synthesis of a series of 1,7-dioxaspirononanes that applies a ketyl radical cyclization strategy is described. Radical cyclization of the β-disubstituted acrylate 23, prepared in five steps from (R)-1,2-isopropylideneglycerol, gives both 2,3-syn- and 2,3-anti-furan products. The densely functionalized furan heterocycles are used to complete a concise formal synthesis of secosyrin 1, a metabolite of Pseudomonas syringae, and the total synthesis of 4-epi-secosyrin 1.

Antibacterial metabolites from Australian macrofungi from the genus Cortinarius.

In this study, ethyl acetate and aqueous fractions from 117 collections of Australian macrofungi belonging to the mushroom genus Cortinarius were screened for antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Overall, the lipophilic fractions were more active than the aqueous fractions. The ethyl acetate fractions of most or all collections of 13 species, namely Cortinarius ardesiacus, C.

Synthesis of pyran and pyranone natural products.

An overview of the synthesis of the fungal metabolites (+)-dermolactone, (-)- semixanthomegnin, (+)- and (-)-mellein, (-)-ochratoxin alpha, (-)-(1R,3S)-thysanone, the enantiopure ventiloquinones L, E and G, and 8-desmethyleleutherin from a common chiral intermediate, is presented. Further methodology leading potentially toward extended quinones such as (3S,3'S)-xylindein is also outlined.

Total synthesis of enantiopure 1,3-dimethylpyranonaphthoquinones including ventiloquinones E, G, L and eleutherin.

A new synthetic approach to enantiopure pyranonaphthoquinones is described. (S)-Mellein 10, prepared in 6 steps from (S)-propylene oxide 16, is converted stereospecifically to the (1R,3S)-dimethylpyran 15. The pyran 15 is then converted to the benzoquinone 14, which undergoes regiospecific Diels-Alder reactions with a variety of oxygenated butadienes to give pyranonaphthoquinones including ventiloquinones E, G, L, eleutherin and ent-deoxyquinone A.