BIOSYNTHETIC ASPECTS AND BIOMIMETIC-LIKE SYNTHESES

On the results up to 1972 a very thorough review has appeared in the book by Flynn [2], which in addition deals with the biochemical background of the appropriate amino adds [262]. A newer review (1976) is that of Sammes [166] which sets out to consider the most probable and important points which can be gained from the ample results and which seem to confirm the tripeptide theory. 

The Cephalosporiunt type biosynthesis differs from the former in some points the fermentation is independent of the given precursor add [269] and no (or only traces of) 6-APA can be detected [270,271]. In contrast to the Penicillium-type biosynthesis, the corresponding 7-ACA does not appear as a product of fermentation. Members of this group are Cephalosporium acremo-nium (or by its newer name Acremomum chrysogenum) and C salmosynnema-tum [272], nthesizing cephalosporin C ((2), R = (290), X = OAc, = H) and penicillin N ((1), R = (290)). 

Various Streptomyces strains yield the important 7-methoxy-cephalosporin C 

The bicyclic skeletons of both the penicillins and cephalosporins can formally be divided into amino acid components, as shown by (291) and (292) this is of importance as regards the tripeptide theory. 

The tripeptide theory followed the isolation of L-a-aminoadipyl-L-cystein-L-valine (LLL-ACV or also called Arnstein-tripeptide) (291) by Arnstein, Morris and Toms [273,274]. Later LLD-ACV was found mslmmoiCephalosporium-type [267,275,276]. Further support for the tripeptide theory emerged with the isolation of isopenicillin N, which could be regarded most probably as the common precursor of 6-APA and the various Af-acylpenicillins [267,268,277, 278], 

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