Tetramic acid biological activity

It is somewhat surprising to find that there have been only three published reviews on tetramic acids. The first reports on the advances in tetramic acid chemistry up to 1993 [1], another describes the synthesis of tetramic acid antibiotics [3], and a third, dealing with the structure, isolation and synthesis of naturally occurring tetramic acids, was published in 1995 [4]. The present review is an attempt to cover the field of tetramic acid metabolites with particular emphasis on the structure, biosynthesis and biological activity of these compounds. 

Besides diketopiperazines, there are two other classes of phytotoxins produced by A. a1ternata on spotted knapweed tetramic acids and perylenequinones (1 ). Both groups of compounds are nonhost specific and require relatively large concentrations for biological activity to be expressed, eg. (IS). These... 

The spectrum of biological activity displayed by tetramic acid-containing natural products is remarkable in its diversity it includes potent antibiotic, antiviral and antiulcerative properties, cytotoxicity and mycotoxicity, the inhibition of tumors (in mice and humans) as well as fungicidal action." Other members of this class are responsible for the pigmentation of certain molds and sponges. 

One of the most toxic components among Alternaria my cotoxins is tenuazonic acid (741) (475) (Fig. 11.4), a tetramic acid derivative, which was first isolated from the culture filtrates of Alternaria tenuis in 1957 by Rosett et al. (476) and shows potent biological activity (475). Tenuazonic acid is biosynthesized from L-fro-leucine and its structure was revealed four years later by Sticicings and his group (477). 

Fuligorubin-A is structurally closely related to several tetramic acids which are known as biologically active metabolites of microorganisms 668). The biological properties of fuligorubin-A have not yet been determined. 

Taken from the jellyfish Aurelia aurita harvested in the North Sea, the species Epicoccumpurpurascens produces in culture a long-chain mannoside with a tetramic acid, epicoccamide. However, this original, and most probably amphiphilic, derivative has no detectable biological activity... 

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