The Diazo Route to Diazonamide A. Studies on the Indole Bis-oxazole Fragment
作者:James R. Davies、Peter D. Kane、Christopher J. Moody
DOI:10.1021/jo0509760
日期:2005.9.1
Various approaches to the indole bis-oxazole fragment of the marine secondary metabolite diazonamide A are described, all of which feature dirhodium(II)-catalyzed reactions of diazocarbonyl compounds in key steps. Thus, 3-bromophenylacetaldehyde is converted into an α-diazo-β-ketoester, dirhodium(II)-catalyzed reaction of which with N-Boc-valinamide resulted in N-H insertion of the intermediate rhodium
描述了海洋次生代谢产物重氮酰胺A的吲哚双恶唑片段的各种方法,所有这些方法均在关键步骤中采用了重氮(II)催化的重氮羰基化合物的反应。因此,将3-溴苯基乙醛转化为α-重氮-β-酮酸酯,其二价吡啶鎓(II)与N -Boc-缬氨酰胺催化的反应导致中间体铑卡宾在NH的插入,从而得到易于进行环脱水反应的酮酰胺。得到(小号)- 2-(1-叔-丁氧基羰基氨基)-2-甲基丙基] -5-(3-溴苄基)恶唑-4-羧酰胺酰胺化后形成的酯。然后在Pd催化下将该芳基溴化物与3-甲酰基-吲哚-4-硼酸酯偶合,得到预期的联芳基。醛基随后转化为第二种α-重氮-β-酮酸酯为分子内卡宾NH的插入提供了底物,尽管进行这种环化的尝试并未成功。吲哚双恶唑的第二种方法涉及插入分子间铑卡宾NH,然后形成恶唑,得到(S)-2- [1-叔丁基-(丁氧基羰基氨基)-2-甲基丙基] -5-甲基恶唑-4-羧酰胺。将该羧化物与衍生自2-重氮-3-