Synthesis of the Natural Products 3-Hydroxymollugin and 3-Methoxymollugin

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• 作者：Mudiganti Naga Venkata Sastry ; Sven Claessens ; Pascal Habonimana ; Norbert De Kimpe
• 刊名：Journal of Organic Chemistry
• 出版年：2010
• 出版时间：April 2, 2010
• 年：2010
• 卷：75
• 期：7
• 页码：2274-2280
• 全文大小：924K
• 年卷期：v.75,no.7(April 2, 2010)
• ISSN：1520-6904

文摘

3-Hydroxymollugin 2 and 3-methoxymollugin 3 are cytotoxic compounds isolated as minor compounds from Pentas longiflora and Rubia cordifolia. Syntheses of 3-hydroxymollugin 2 and 3-methoxymollugin 3 were developed starting from easily available 3-bromomollugin 6. Surprisingly, it was found that the reaction of 3-bromomollugin 6 with sodium methoxide in methanol resulted in the formation of 3-methoxymollugin 3 and the ring-contracted methyl isopropenylfuromollugin 7. A mechanism for this ring contraction is proposed on the basis of a pericyclic retro oxa-6π ring-opening reaction. A second synthesis of 3-hydroxymollugin 2 was based on epoxidation of methyl 3-(3-methylbut-2-enyl)-1,4-naphthoquinone-2-carboxylate 17 and subsequent reduction of the quinone moiety, ring transformation, and DDQ oxidation. The latter oxidation process results in 3-hydroxymollugin 2 along with the rearranged furomollugin 4, which is a ring-contracted analogue of the natural product mollugin 1.