Chemoenzymatic total syntheses of the linear triquinane-type natural products (+)-hirsutic acid and (−)-complicatic acid from toluene |
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Authors: | Martin G Banwell Kerrie AB Austin Anthony C Willis |
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Institution: | Research School of Chemistry, Institute of Advanced Studies, The Australian National University, Canberra, ACT 0200, Australia |
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Abstract: | Total syntheses of title natural products, 1 and 2, have been achieved using the cis-1,2-dihydrocatechol 7 as starting material. Compound 7 is readily obtained in large quantity and enantiomerically pure form through the whole-cell biotransformation of toluene using the genetically engineered micro-organism Escherichia coli JM109 (pDTG601) that over-expresses the enzyme toluene dioxygenase (TDO). Three key chemical steps were employed in these syntheses, the first of which was a high-pressure-promoted Diels-Alder cycloaddition reaction between diene 8 and cyclopentenone to give adduct 9. The second key step was the photochemically promoted oxa-di-π-methane rearrangement of the bicyclo2.2.2]octenone derivative, 18, of 9 to give 20 while the third key step was the reductive cleavage of the last compound so as to afford the linear triquinane 22. Elaboration of compound 22 to targets 1 and 2 followed conventional and/or established procedures. Single-crystal X-ray analyses were carried out on compounds 10-13, 15, 18, 24, and 34. |
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Keywords: | Chemoenzymatic (&minus )-Complicatic acid Diels-Alder reaction cis-1 2-Dihydrocatechol (+)-Hirsutic acid Oxa-di-π-methane rearrangement Sesquiterpene Triquinane |
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