Synthesis of a para-quinone macrolactam related to geldanamycin by ring closing metathesis |
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Authors: | Aude Lemarchand |
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Institution: | Lehrstuhl für Organische Chemie I, Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany |
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Abstract: | Model studies conducted with the α,β,γ,δ-unsaturated 3-alkenyl-2,4,5-trimethoxyanilides 11 revealed that a ring closing metathesis (RCM) of these compounds is possible if the ansa chain contains more than 14 atoms. The (Z)-configurated products 12c-e were obtained in good yields (77-87%) and with perfect simple diastereoselectivity. Since the oxidation of the 2,4,5-trimethoxyanilides led predominantly to undesired ortho-quinones such as 15 or to para-azaquinones such as 16 the macrocyclic 2,5-di-iso-propoxy-4-methoxyanilide 22 was prepared. The iso-propyl protecting groups could be selectively cleaved and the intermediate para-hydroquinone oxidized on air to the desired para-quinone 2 (86% yield). The compound shows some key features (macrolactam ring with the same ring size, α,β,γ,δ-unsaturated anilide, para-quinone) of geldanamycin. |
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Keywords: | Ring closing metathesis Ansa chain Geldanamycin |
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