A practical and concise total synthesis of tricyclic ketone 7 (CDE ring), a valuable intermediate for the synthesis of racemic camptothecin and analogs, was described (8 chemical steps and 29% overall yield). The synthesis starts with two inexpensive, readily available materials and is operationally simple to perform. It is worth mentioning that the reported protecting group-free synthesis, with advantages of a short route, would be helpful for the future development of industry-scale syntheses of camptothecin-family alkaloids.

中文翻译：

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外消旋喜树碱CDE合成子的短保护基无保护基合成。

描述了一种实用而简明的全合成三环酮7（CDE环），它是合成外消旋喜树碱及其类似物的重要中间体（8个化学步骤，总收率29％）。合成从两种廉价，易于获得的材料开始，并且操作简单。值得一提的是，报道的具有保护途径的无保护基团的合成具有短路径的优势，将有助于喜树碱家族生物碱的工业规模合成的未来发展。