INVESTIGATIONS OF THE BIOSYNTHESIS AND STRUCTURAL REVISION OF LANDOMYCIN-A

Feeding experiments with [1-C-13]-, [1,2-C-13(2)]-, and [1-C-13,O-18(2 )]acetate as well as a fermentation under an O-18-enriched atmosphere resulted in information regarding the biosynthetic origin of all carbo n and of the oxygen atoms of the landomycin A aglycon moiety as well a s of the direction of the incorporation of the decaketide chain. Only two of the six oxygens in landomycinone seem to originate from the ace tate building blocks. This raises questions about current hypotheses f or the formation of multicyclic aromatic polyketides. Some unusual pre aromatic deoxygenation steps early in the biosynthesis have been propo sed. As an additional result of the biosynthetic investigations, the s tructure of landomycin A and thus of all other landomycins were revise d concerning the position of the phenol-glycosidically linked deoxysac charide chain from 2 to 1.