73 新しいマイトマイシンの化学 : イソマイトマイシンAのマイトマイシンAからの変換(ポスター発表の部)

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Albomitomycin A (2) and isomitomycin A (3) are quite attractive because of their biological activity, molecular structure and chemical reactivity. They were unfortunately minor components of the culture broth of Streptomyces caespitosus, therefore, an effective preparation of them has been desired. To fulfil this demand, we have developed new mitomycin chemistry described below. Based on the X-ray crystallographic analysis of mitomycin A (1) and 2, the chemical conversion of 1 to 3 via 2 was accomplished in 68% overall yield. First, the distance between C4a and N1a of 1, that was 3.32Å, suggests that the cyclization between these two atoms should occur easily. Indeed, 1 was smoothly converted to 4a and 4b on treatment with NBS in quantitative yield. Then 4a and 4b afforded to 2 in 56% and 54% yield, respectively, accompanying with 1 under hydrogenolysis condition. Additionally, 4a was isomerized to 4b on treatment with K_2CO_3 in 89% yield, and then 4b was reduced to 2 with n-Bu_3SnH / AIBN in 85% yield. Next, the inspection of dihedral angle of O5-C5-C4a-N4 of 2 suggests that the C4a-N4 bond of 2 should be more easily hydrogenated than C4a-N1a bond by the assist of C5 carbonyl. Actually, the C4a-N4 bond was selectively cleaved, and consecutive air oxidation gave 3 in 90% yield from 2. The usefulness of 2 and 3 for the synthesis of mitomycin derivatives was shown by direct conversion of them to mitomycin C. The new chemistry which was established by the present study, will certainly open the new era of mitomycin chemistry.
天然有機化合物討論会の論文
1990-09-25

73 新しいマイトマイシンの化学 : イソマイトマイシンAのマイトマイシンAからの変換(ポスター発表の部)

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