Oudemansin A is a

natural product A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical s ...

first isolated from the basidiomycete fungus ''

Oudemansiella mucida ''Oudemansiella mucida'', commonly known as porcelain fungus, is a basidiomycete fungus of the family Physalacriaceae and native to Europe. ''O. mucida'' is a white, slimy wood-rot fungus and is strongly tied to rotting beech, where it grows in ...

''. Its chemical structure was determined by X-ray crystallography in 1979 and

absolute stereochemistry In chemistry, absolute configuration refers to the spatial arrangement of atoms within a molecular entity (or group) that is chiral, and its resultant stereochemical description. Absolute configuration is typically relevant in organic molecules ...

by total synthesis. Two closely related derivatives, oudemansin B and X have also been isolated from other basidiomycetes. They are all

biologically active In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or p ...

against many filamentous fungi and yeasts but with insufficient potency and stability to become useful commercial products. However, their discovery, together with the

strobilurins Strobilurins are a group of natural products and their synthetic analogs. A number of strobilurins are used in agriculture as fungicides. They are part of the larger group of QIs (Quinone outside Inhibitors), which act to inhibit the respiratory ch ...

led to agricultural fungicides including

azoxystrobin Azoxystrobin is a broad spectrum systemic fungicide widely used in agriculture to protect crops from fungal diseases. It was first marketed in 1996 using the brand name Amistar and by 1999 it had been registered in 48 countries on more than 50 cr ...

with the same mechanism of action.

Isolation and characterization

Oudemansin A (initially known simply as oudemansin) with R₁ = R₂ = H was first described in 1979, after being isolated from mycelial fermentations of the

basidiomycete Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basid ...

fungus ''

''. Its structure, including the relative configuration of the methoxy and adjacent methyl groups, was established by both spectroscopic methods and single crystal X-ray analysis but its absolute stereochemistry was at that time undetermined. Later it was found in cultures of the basidiomycete fungi ''

Mycena polygramma ''Mycena polygramma'', commonly known as the grooved bonnet, is a species of mushroom in the family Mycenaceae. The inedible fruit bodies are small, pale gray-brown mushrooms with broadly conical caps, pinkish gills. They are found in small tr ...

'' and ''Xerula melanotricha''. The latter fungus also produces oudemansin B, with R₁ = MeO and R₂ = Cl. Oudemansin X, with R₁ = H and R₂ = MeO was isolated from ''

Oudemansiella radicata ''Hymenopellis radicata'', commonly known as the deep root mushroom, beech rooter, or the rooting shank, is a widespread agaric readily identified by its deeply rooted stalk ( stipe). Description The cap is medium to large, flat, grayish or y ...

''.

Chemical synthesis

The oudemansins have been targets for total synthesis and in 1983, the synthesis of (-)-oudemansin A established that all three compounds have the (9''S'',10''S'')-

configuration Configuration or configurations may refer to: Computing * Computer configuration or system configuration * Configuration file, a software file used to configure the initial settings for a computer program * Configurator, also known as choice board ...

. Routes to oudemansins B and X have also been reported.

Mechanism of action as fungicides

The fungicidal effects were shown to stem from what was then a novel mode of action, QoI inhibition. This was related to the β-methoxyacrylic acid sub-structure which this and related natural products, the

strobilurin Strobilurins are a group of natural products and their synthetic analogs. A number of strobilurins are used in agriculture as fungicides. They are part of the larger group of QIs (Quinone outside Inhibitors), which act to inhibit the respiratory ch ...

s have in common. Intensive research by several agrochemical companies led to the development of useful agricultural fungicides based on the same mode of action, of which

is a typical example.

Isolation and characterization

Chemical synthesis

Mechanism of action as fungicides

References

Further reading