40 ハービマイシンAの全合成(口頭発表の部)

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The benzoquinoid ansamycin antibiotic herbimycin A (1) was isolated in 1979 from the fermentation broth of Streptomyces hygroscopicus strain AM-3672. It exhibits herbicidal, antitabacco mosaic virus, and antitumor activities. The structure of 1 was elucidated by spectroscopic and biosynthetic means and the relative configuration of 1 was established by X-ray crystallographic analysis. We now report the first total synthesis of herbimycin A (1) and elucidate the absolute stereochemisrty of 1. Herbimycin A (1) was divided into two portions, namely the ansa-chain aldehyde 2 and the aromatic chromophore 3. The epoxide 10, which was prepared from methyl α-D-mannopyranoside 4 according to our developed procedure, was transformed to the C7-C15 aldehyde 23 by using a regioselective epoxide-ring opening (disiamylborane-NaBH_4) and a stereoselective hydroboration (BH_3・Me_2S) as the key steps. This aldehyde 23 was subjected to the Brown's diastereo- and enantioselective allylation conditions [[(Z)-γ-methoxyallylidiisopinocampheylborane prepared from (-)-α-pinene] to afford the desired syn-type compound 24. After a three-step sequence, 24 was converted to the ansa-chain aldehyde 2. This ansa-chain aldehyde 2 was coupled with the lithiated aromatic chromophore (prepared from 3 and n-BuLi) to produce the coupling product 26, which was transformed to herbimycin A (1) through elongation of the C1〜C4 carbon unit and macrolactamization. All data (^1H NMR, IR, UV, [α]_D, and TLC mobilities) were identical with those of natural herbimycin A.
天然有機化合物討論会の論文
1991-09-07

40 ハービマイシンAの全合成(口頭発表の部)

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