Cyclizidine

The microbial metabolite cyclizidine (60), introduced in Volume 28 of this treatise (7), was originally isolated from a Streptomyces strain found in a hedgerow soil sample in the United Kingdom 49). It has since been isolated by Chinese workers from the fermentation broth of Streptomyces strain L-892 50). 

Figure 3.83 Structure of cyclizidine and mdolizomycin and C- and H-labeling patterns from the incorporation of [l- C]acetate, [l,2- C]acetate, [l- C]propionate, [S- Hjipropionate, and [l- C, 02]acetate.

The biosynthesis of indolizomycin 297 has not been studied, but its structural similarity to cyclizidine 296 makes it probable that it has a similar biosynthesis. However, the branched four-carbon unit of 297 which replaces the cyclopropyl group of 296 cannot be directly produced by a polyketide route. By analogy with the biosynthesis of cyclizidine, it is conceivable that these four carbons are derived from two acetate units by a rearrangement involving an intermediate cyclopropane ring [295]. 

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