83(P-14) 5(4)-Alkenylimidazole類の新規Diels-Alder二量化反応を鍵とする生理活性海洋天然物Ageliferinsの全合成研究(ポスター発表の部)

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Recently, many types of biologically active pyrrole-imidazole alkaloids have been isolated from marine lives such as sponges, and they have become a focus of scientific attentions. Ageliferins 1-3 were isolated in 1990 from Agelas sponges and found to have various biological activities such as actomyosin ATPase, antiviral and antibacterial actions. We have investigated total syntheses of various biologically active imidazole alkaloids, and in this time, we would like to present the first synthesis of 12,12'-dimethylageliferin 20 through a Diels-Alder dimerization of 5-alkenylimidazole 9a as a key step. Various 5(4)-alkenylimidazoles 8-9 were prepared, and their Diels-Alder dimerization toward 4,5,6,7-tetrahydrobenzimidazoles 10 under thermal reaction conditions was examined. When the acrylate 9a was refluxed in xylene for 30h, the expected dimer 10d was obtained as major product in 54% chemical yield and 98% diastereo selectivity. The structure of 10d was confirmed by HMBC and NOESY experiments. This novel Diels-Alder dimerization reaction provides a highly regio- and stereoselective route to the preparation of the multifunctionalized 4,5,6,7-tetrahydrobenzimidazoles, and synthesis of 12,12'-dimethylageliferin 20 was achieved by using 9 steps conversion from the diester 10d.
天然有機化合物討論会の論文
2002-09-01