Chapter 14. Biosynthesis of Antibiotics

Abstract

Publisher Summary The powerful methods for the determination of a new structure of biosynthesis of natural products, including antibiotics, are discussed in this chapter. The hydroxymethyl branch group of the dihydrostreptose moiety is oxidized either before or after the addition of the glucosamine fragment when streptomycin phosphate is the product. The biogenesis of the polyene macrolide candicidin is from acetate and propionate with the additional presence in the structure of aminoacetophenone and mycosamine; biosynthesis of the candidin and candihexin complex via sugar-free aglycones within the producing mycelium. Glycosylation takes place during the secretion of the final products. Glycosylation occurs during the biosynthesis of tetracyclines and related antibiotics. The glutarimide antibiotic streptimidone is formed from seven malonate units and is in itself unusual by having the polyketide synthesis initiates by a malonate unit that is retained intact in the final structure. Coupling of the isoprenoid and polyketide pathways occurs in the biogenesis of siccanin 48 from trans-y-monocyclofarnesol and orsellinic acid. The biosynthesis of chloizaiwhenicol has led to the conclusion that it is formed via the shikimic acid pathway specifically from chorismic acid. The novel new antibiotic nybomycin possesses both fused pyridoquinolone and angularly fused oxazoline ring systems are formed from both the acetate and shikimate plus a methyl group from methionine. A step in the biosynthesis of patulin is clarified by finding that the meta hydroxy benzyl alcohol is hydroxylated to yield gentisyl alcohol that in turn is converted to patulin via the aldehyde.