A simple approach towards the pyrido[1,2-a:3,4-b′]diindole system via the reaction of indigo with methylene active compounds was used for the syntheses of the marine alkaloids 6-oxofascaplysin, fascaplysin, and their derivatives. It was also demonstrated that the reaction with ketones led to indigo decomposition and the formation of isatin derivatives. The derivative of fascaplysin with a phenyl substituent at C-7 demonstrated 2–3 times greater inhibitory activity against selected cancer cell lines than fascaplysin.

中文翻译：

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海洋生物碱6-氧天冬青素，法西林素及其衍生物的合成

通过靛蓝与亚甲基活性化合物反应制得吡啶并[1,2- a：3,4- b ']二吲哚系统的一种简单方法是用于合成海洋生物碱6-oxofascaplysin，fascaplysin及其衍生物。还证明了与酮的反应导致靛蓝分解和靛红衍生物的形成。具有在C-7处有一个苯基取代基的fascaplysin衍生物对Fascaplysin的抑制作用是对fascaplysin的2-3倍。