Pyrenochaetic acid

The formation of aromatic rings via rDA processes has found application in the synthesis of many natural products only a representative set can be presented here. Pyrenochaetic acid A (134), a phytotoxic metabolite, was synthesized by a process involving a rDA reaction as a key step. The DA reaction of pyrone (132) with ethyl propiolate gave, after isolation, benzoate (133) via a rDA reaction evolving carixin dioxide (equation 60). A synthesis of a-cartopterone (137) has been achieved that involves the rDA elimination of ethylene. The tey step is rDA decomposition of adduct (135) to naphthoquinone... 

In the course of phytotoxin research, pyrenocines A (85) and B (86), and pyrenochaetic acids A (87), B (88) and C (89), were isolated from the culture filtrate of Pyrenochaeta terrestris, causal fungus of onion pink root disease, Fig. 22 [62, 63]. After structural determination, chemical syntheses of these phytotoxins were attempted [64-66]. Alth-... 

Fig. 23. Synthesis of pyrenochaetic acid A (87) through the Diels-Alder and retro Diels-Alder reactions...

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