Ketide side-chains

In the laboratory of K. Krohn, the total synthesis of akianonic acid and its derivatives was undertaken, utilizing the Baker-Venkataraman rearrangement of ort/70-acetyl anthraquinone esters in the presence of lithium hydride. Using this method, it was possible to introduce ketide side-chains on anthraquinones in a facile manner. 

Biosynthetic studies showed that the aromatic ring was formed from a poly-ketide whilst the side chain was derived from the mevalonate terpenoid pathway. The C-5 O-methyl and C-4 methyl groups were derived from methionine. The high incorporation of 4,6-dihydroxy-2,3-dimethyl-[l- C]benzoic acid (4.37) suggested that the methylation at C-4 occurred at the polyketide stage prior to the formation of the phthalide. 5,7-Dihydroxy-4-methyl-[7- C]phthalide (4.38) and its 6-farnesyl analogue were also incorporated eiSciently into mycophenolic acid. The farnesyl precursor was detected as a metabolite of P. brevi-compactum and shown to be formed from 5,7-dihydroxy-4-methyl-[7- C]phthalide by a trapping... 

Seven lasonolide series (A, B, C, D, E, F, G) [37] of natmal products have been isolated to date, all of which possess the same C-1 through C-29 poly-ketide, but differ in the nature of the side-chain substituents (Fig. 2). The... 

The carbon skeleton of maltoryzine appears to be derived from poly-ketide 12. The oxygenation pattern in the phenol ring and side chain of this compound, however, differed from the general biogenetic principles of polyketide formation (Turner, 1971). No evidence to support the biosynthesis of maltoryzine has yet been obtained. 

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