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The total synthesis of (+/-)-aspirochlorine




Miknis, Gregory Francis, author
Williams, Robert M., advisor

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Aspirochlorine is a unique epidithiodioxopiperazine isolated from Aspergillus oryzae, Asp. tamarii and Asp. flavus. The molecule contains a highly unusual bicyclo [3.2.2]disulfide ring system which has previously never been prepared. The first total synthesis of (±)-Aspirochlorine was achieved from commercially available 5-chlororesorcinol 324 in 16 steps. The key step in the synthesis was an efficient intramolecular cycloaddition reaction of hydroxamic ester 344 to form the parent spiro [benzofuran-2(3H),2'-piperazine] ring system 345 as a single stereoisomer. In addition the synthesis employed a 2-nitrobenzyl moiety as a novel amide protecting group. The 2-nitrobenzyl group could be removed in 72% yield under photolytic conditions. Synthetic aspirochlorine was identical to natural material in comparison by 1H NMR, IR and HPLC. Comparison of the biological activity of aspirochlorine versus other epidithiodioxopiperazines was investigated as a function of superoxide production. Although aspirochlorine was shown to be capable of producing superoxide as evidenced in DNA plasmid nicking and NBT reduction assays, the observed activity was less than the 6-membered epidithiodioxopiperazines.


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Fungal metabolites


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