SIRODESMIN BIOSYNTHESIS

Using DL-[3,5-H-3, U-C-14]tyrosine it is shown that in the biosynthesis of sirodesmins all nine carbon atoms of tyrosine are incorporated into the rearranged structure. Using [(C2)-C-13]acetate it is confirmed that the biosynthesis proceeds by way of a type of Claisen rearrangement of an O-(3,3-dimethylallyl)tyrosine derivative, and the chirality of this rearrangement is established. The order and stereochemical implications of other steps in the biosynthesis are considered.