74(P-63) Kinamycin系抗生物質の合成研究(ポスター発表の部)

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Kinamycin antibiotics and prekinamycin, produced by Streptomyces murayamaensis, were firstly proposed to be composed of N-cyanobenzo[b]carbazoloquinone skeletons. After that, the ring systems were revised to be benzo[b]fluorene skeletons with diazoalkane moiety based on synthetic studies and re-examination of their spectral data. However, the revised structure of prekinamycin was not identical with natural product, instead, an isomeric benzo[a]fluorene skeleton was proposed for the natural product, which was newly named as isoprekinamycin. We have started to synthesize the revised structure 2a of kinamycins for due to these structural confusions. Our synthetic strategy is as follows: synthesis of benz[f]indenone 5 and the Diels-Alder reaction with diene 6 followed by the elaboration of a highly oxygenated D ring. We tried the elaboration of D ring using a model indenone 7. Diels-Alder reaction of 7 and diene 6 followed by acid hydrolysis and oxygenation gave hydroxyketone 11. Hydroxylation and then stereoselective reduction gave tetraol 13. Dihydroxylation of TBS ether of 13 gave triol 17 with desired configurations on D ring. Dehydration followed by introduction of diazo moiety led to the successful synthesis of 9-diazofluorene 24. We next turned to the synthesis of 2a. Benz[f]indenone 5 was prepared by cyclization of 28, derived from bromonaphthalene 25, followed by oxidation with IBX. Successive reactions of Diels-Alder reaction with 5 and 6, acid hydrolysis and oxygenation afforded hydroxyketone 30. syn-Selective dihydroxylation of 30 followed by hydroxylation gave tetraol 34a, which was reduced with Me_4NBH(OAc)_3 to yield the expected pentaol 36.
天然有機化合物討論会の論文
2003-09-01

74(P-63) Kinamycin系抗生物質の合成研究(ポスター発表の部)

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